Class 10th mathematics

Tricks to remember Trigonometric Angles : Notes For Class 10th NCERT

An Introduction to Trigonometry

Basic Definition – Trigonometry is a branch of mathematics which deals with the relationship between the sides and the angles of right-angled triangles. Here the term ‘Right-angled’ triangle is very important.

Let’s understand this with an example.

Consider a girl looking at the top of a tower which is few distances apart from her legs. Now, this will form a right-angled triangle whose height can be calculated without actually measuring it physically.

In this chapter, we will be learning about some standard trigonometric identities by using the relation between angles and the sides of the right-angled triangle.

# Trigonometric Ratios-

C:\Users\Vishesh Meena\Downloads\download (1).png

  • Consider a right triangle with sides AB, BC and AC with C as a right angle.
  • Now, considering an acute angle let’s say Angle A, then side opposite to A i.e. a is called the hypotenuse. Also, side b is called the adjacent side.

The trigonometric ratios are defined as:

These ratios are generally represented in their short forms. These are sin A, cos A, tan A, cosec A, sec A and cot A respectively.


  1. cosec A, sec A and cot A are the inverse of sin A, cos A and tan A respectively.
  2. sin A /cos A = tan A and therefore cos A/sin A = cot A

Example 1: Given sinA =4/5, Find all other trigonometric ratios of angle A.

Solution: Let’s draw a right triangle ∆ABC right angled at B.

Now, Given that sin A =4/5

∴BC/AC =4/5
∴ BC = 4k and AC= 5K, where K is a constant.

Now, In ∆ABC, applying Pythagoras Theorem,

(AC)2 = (AB)2 + (BC)2

∴ (5K)2 = (AB)2 + (4K)2

∴ AB = 3K





Similarly, cosec A = 1/ sin A = 5/4
And, sec A = 1/ cos A = 5/3
And, cot A = 1/ tan A = 4/3 Answer

Trick To Remember All the Trigonometric Ratios 

We will remember all the ratios using a mnemonics as 

Pandita Badri Prasad
Hara     Hara   Bola 


Here Look at the ratios and the words

  • For Sin theta, we have Pandita/Hara which is P/H
  • Similarly For Cos theta we have Badri/hara which is B/H
  • Similarly for Tan theta, we have Prasad/Bola which P/B
  • For other ratio take the reciprocal of the angles.
  • Such as for Cosec theta it is H/P
  • Sec Theta it is H/B and for Cot theta, it is B/P.

This note is Contributed by 
Vishesh Meena
3rd Year, Electrical Engineering,
[email protected]

Class 9 Science

Newton’s First Law of Motion : Explained


Newton’s first law ( law of inertia) :

  • The famous Newton’s laws of motion are basically always the starting point in learning mechanics (a branch of physics) but the observations of the first law were actually made by scientist Galileo Galilei; Newton just studied those observations and presented three laws of motion and are thus named as Newton’s laws of motion.


  • In the above pictures we observe a simple experiment in which glass is mounted by a sheet of paper.
  • We place a metal coin on that sheet of paper.
  • When we apply slight force to the sheet of paper the paper moves as expected but the surprising observation was that the coin instead of moving with paper simply falls perpendicular into glass with respect to its original position.
  • Why does this happen?
  • Galileo observed that when a marble rolls down an inclined plane it’s velocity increases.
  • One would expect the ball to keep moving horizontally forever trying to achieve the same height from which it was released but we don’t find this happening in our practical lives because of frictional or other forces acting on that marble.
  • Thus, after studying all these observations Newton formulated three laws of motion.
  • The first law states that :

An object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.


In simple words, all objects resist a change in their state of motion which means that than object at rest would prefer to stay at rest and an object in motion would prefer to stay in uniform motion unless acted upon by an external force.

  • The property that we observe here is called inertia which is defined as the natural tendency of an object to resist a change in its state of motion or of rest.

Some common day to day examples that we observe regarding this law are:

  1. When a car is moving with uniform velocity and suddenly brakes are applied then we experience a push in the forward direction i.e., the direction of motion of car. This is because our body in was in uniform motion and thus is resisting to change its state of motion. In such situations the seat belt worn by us exerts force on our bodies in opposite direction thus preventing our bodies to move forward in case of sudden brakes. This is also the reason why seat belts are compulsory.

  1. Now, suppose a train is at rest and suddenly it starts. The passengers in train will experience a jerk backwards due inertia.Therefore the train always first starts at very slow speed and then step by step increases it speed.
  2. You are sitting in a merry go round and it is moving with high speed. In such case you tend to experience a force pulling you outside. This is again due to inertia but instead of jerk you feel a constant force pulling you outside because merry go rounds are always circular and the direction of force changes at every point in a circle (reason is that the direction of force is given by a tangent in circle and the tangent changes at every point).
  • Another important point to note is that inertia depends on mass because the force required to stop a bicycle moving in uniform motion is definitely much lesser than force required to stop a moving train.
Class 10th Science

Explained : Nomenclature of Carbon Compounds


  • Organic compounds are the compounds mainly consisting of C and H atoms , along with some atoms like O,N, Halogens occasionally.
  • An organic compound in general will have two names – common name and IUPAC name.
  • IUPAC (International Unit of Pure and Applied Chemistry) nomenclature are the standard names.
  • The common name is based on the source or some properties.
  • For e.g. Citric acid is named so because it is found in citrus fruits and the acid found in red ant is named formic acid since the Latin word for ant is formica.
    ant - formica (formic acid)
    ant – formica (formic acid)

    lemon- citrus (citric acid)
    lemon- citrus (citric acid)

We will study IUPAC nomenclature in detail .


  • A systematic name of an organic compound is generally derived by identifying the parent hydrocarbon and the functional group(s) attached to it.
  • This name is called IUPAC name.
  • It contains two parts – word root and suffix or prefix.
  • The word root indicates the number of carbon atoms in the compound.
  • The word roots for compounds containing 1 -12 carbon atoms are as follows:
No. of C atoms Word root No. of C atoms Word root
C1 Meth- C7 -Hept
C2 Eth- C8 -Oct
C3 Prop- C9 -Non
C4 But- C10 -Dec
C5 Pent- C11 -Undec
C6 Hex- C12 -Dodec



There are two types of suffixes :

  • primary suffix  and secondary suffix
  • Primary suffix indicates saturation or unsaturation [for alkane the primary suffix is –ane, alkene –ene and for alkyne –yne].
  • Secondary suffix indicates the type of functional group. Some functional groups are also indicated as prefixes.

Nomenclature of branched chain alkanes

  • A branch (side chain or substituent) is obtained by removing a hydrogen atom from an alkane. The resulting group is called an alkyl group [alkane]
  • – H = alkyl (i.e. word root + yl)].

The names of some common branches are as follows:

Branch Name
-CH3 Methyl
-CH2-CH3 Ethyl
-CH2-CH2-CH3 n-propyl (normal propyl)
(CH3)2CH- isopropyl
-CH2-CH2-CH2-CH3 n-butyl


sec-butyl (secondary butyl)
(CH3)2CH-CH2 isobutyl

Rules for naming branched chain alkanes:

IUPAC recommenced the following rules for naming a branched chain alkane.

  1. Select the longest continuous chain of carbon atoms.
  2. This chain is called parent chain or root chain.
  3. If there is more than one such chain, the chain that contains maximum number of branches is selected as the parent chain.
  4. Also identify all the branches or substituents.
  5. Number the carbon atoms of the parent chain in such a way that the branched carbon atoms get the lowest possible numbers.
  6. The names of alkyl groups attached as branches are then prefixed to the name of the parent alkane and position of the substituents is indicated by the appropriate numbers.
  7. If different alkyl groups are present, they are listed in alphabetical order.
  8. In alphabetical order, the prefixes iso- and neo- are considered to be the part of the fundamental name of alkyl group.
  9. The prefixes sec- and tert- are not considered to be the part of the fundamental name.
  10. If two or more identical substituent groups are present then their numbers are indicated by prefixes like di (for 2), tri (for 3), tetra (for 4), penta (for 5) etc. and the numbers are separated by commas.
  11. The number and word are separated by a hyphen. (The IUPAC name is written as a single word).

For example:

  • If the two substituents are found in equivalent positions, the lower number is given to the one coming first in the alphabetical listing. For example:
  • The above compound is 3-ethyl-6-methyloctane and not 6-ethyl-3-methyloctane.
  • While naming the branched alkyl groups, the carbon atom of the branch that attaches to the root alkane is numbered 1.

IUPAC nomenclature of compounds containing functional groups

For naming organic compounds containing functional group, the following rules are used:

  1. Select the longest continuous chain containing the functional group.
  2. Number the carbon atoms in such a way that the carbon to which the functional group is attached should get the lowest possible number.
  3. In the case of functional groups containing carbon atom like –CHO, -CN, – COOH, -CONH2, -COX. -COOR etc. the numbering should start from the carbon atom of the functional group.
  4. (i.e. carbon atom of these groups should be numbered as 1).
  5. (But for ketones, the functional group –CO- should get the lowest possible number).
  6. The name of some of the functional group is indicated by the following suffix or prefix.
  7. In the case of suffixes, the ending –e of the corresponding alkane is replaced.
  8. E.g. IUPAC name of the alcohol CH3-OH is methanol (methane + ol).
  9. But for nitriles, the –e of the corresponding alkane is retained.
  10. E.g. IUPAC name of CH3-CH2-CN is propanenitrile.
  11. In the case of alkenes and alkynes, the suffix –ane of the alkane is replaced by –ene and –yne respectively. (i.e. word root + ene or yne).
  12. For naming alkenes or alkynes, the numbering is done in such a way that the double or triple bond should get the lowest possible number.
  13. Some examples are:

CH3-CH2-CH=CH2 → 1-Butene

Nomenclature of organic compounds containing more than one

functional groups (Poly functional compounds)

  • Here one of the functional groups is chosen as the principal functional group and the compound is named on that basis.
  • The remaining functional groups (called subordinate functional groups) are named as substituents using the appropriate prefixes.
  • The choice of principal functional group is made on the basis of order of preference.
  • The order of decreasing priority for some functional groups is: -COOH, –SO3H, -COOR (R=alkyl group), -COCl, -CONH2, -CN,-CHO, >CO, -OH, -NH2, >C=C<, -C≡CThe groups like alkyl (–R), phenyl (C6H5-), halogens (F, Cl, Br, I), nitro (–NO2), alkoxy (–OR) etc. are always prefix substituents.
  • For example if a compound contains both alcoholic and aldehydic groups, it is named as hydroxyalkanal, since here aldehydic group is the principal functional group and –OH group is the subordinate functional group.
  • The prefix names of some functional groups are as follows:

  • If a compound contains more than one same functional group, their number is indicated by adding the numeral prefixes di, tri, etc. before the suffix.
  • In such cases the full name of the parent alkane is written before the suffix.
  • However, the ending – ne of the parent alkane is dropped in the case of compounds having more than one double or triple bonds.

Nomenclature of Substituted Benzene Compounds

  • For IUPAC nomenclature of substituted benzene compounds, the substituent is placed as prefix to the word benzene.
  • But common names of some compounds are accepted by IUPAC.

Some examples are;

mono substituted Benzene derivatives
mono substituted Benzene derivatives

Nomenclature of di or polysubstituted benzene

  • If benzene ring is disubstituted, the position of substituents is indicated by numbering the carbon atoms of the ring such that the substituents get the lowest possible numbers.

Example – Dibromobenzene

Di bromo derivatives of Benzene
Di bromo derivatives of benzene
  • In the common system of nomenclature the terms ortho (o), meta (m) and para (p) are used as prefixes to indicate the relative positions 1,2- 1,3- and 1,4- respectively.
  • So 1,2-dibromobenzene is named as ortho (or just o-) dibromobenzene, 1,3-dibromobenzene as meta (or just m-) dibromobenzene and 1,4-dibromobenzene as para (or just p-)-dibromobenzene.
  • For tri – or higher substituted benzene derivatives, these prefixes cannot be used and the compounds are named by identifying substituent positions on the ring by following the lowest locant rule.
  • In some cases, common name of benzene derivatives is taken as the base compound.
  • Substituent of the base compound is assigned number1 and then the direction of numbering is chosen such that the next substituent gets the lowest number.
  • The substituents are named in alphabetical order.
1-chloro-2,4-dinitro benzene.
1-chloro-2,4-dinitro benzene.


Blog Class 10th Science

Sex Determination In Human Beings Explained

Sex Determination in Human Beings 

  • A person can have a male sex or a female sex.
  • The process by which the sex of a person is determined is called sex determination.
  • Genetics is involved in the determination of the sex of a person.
  • The chromosomes which determine the sex of a person are called sex chromosomes.
  • There are two types of sex chromosomes, one is called X chromosome and the other is called Y chromosome.
  • Somatic cells in human beings contain 23 pairs of chromosomes.
  • Out of them the 23rd pair is composed of different types of chromosomes which are named as X and Y chromosomes.

Heredity Evolution,Speciation Notes on Science For Class 10th

  • The 23rd pair contains one X and one Y chromosome in a male.
  • On the other hand, the 23rd pair in a female contains X chromosomes.
  • This means that all the eggs would have X chromosome as the 23rd chromosome,
  • While a sperm may have either X or Y chromosome as the 23rd chromosome.
  • When a sperm with a chromosome fertilizes the egg.
  • The resulting zygote would develop into a female child.
  • When a sperm with Y chromosome fertilizes the egg, the resulting Zygote would develop into a male child

Check Out the detailed notes and previous year questions here

Heredity and Evolution NCERT Solutions For Class 10th SCIENCE


Control And Coordination Notes For Class 10th Science

Control and coordination


Animal – nervous system

  • what is nervous system
  • structure and function of neurons
  • reflex arc: definition, component, location, function, examples

Human brain

  • difference between central nervous system and peripheral nervous system
  • brain: different parts, functions of different part of brain

Coordination in plants

  • introduction
  • Definition with examples of different terms used in plants movement
  • Plant hormones- types and functions
  • Hormones in animals

Nervous system-:

  • Coordination is the process through which two or more organs interact and complement the functions of one another.
  • The neural system of all the animals is composed of specialized cells called neurons which can detect, receive and transmit different kinds of stimuli through electrical impulses from one part of body to another.
  • A neuron is a microscopic structure composed of three major parts-

Cell body- it is the spherical part contain nucleus and connect to dendrites on upper side and to axon to the down side.

Dendrites- they receive the stimulus and generate the electrical impulse.

Axon- impulse travel through dendrite to the cell body then axon fragment to its end. At the end of axon, the electrical impulse releases some chemicals.

These chemicals cross the synapse, and start a similar electrical impulse in the dendrite of the next neuron.




  • The process of detecting the signals or the input and responding to it by an output action might be quickly. Such a connection is commonly called a reflex arc.
  • Reflex arc are formed in spinal cord .
  • Reflex arc evolved in animal because the thinking process of brain is not fast enough

Component of reflex pathway

  1. Receptor organ -which get the stimulus ex heat, pain, cold, electric current
  2. Sensory neurons- receives signal from receptor organ and transmit the impulse to spinal cord.
  3. Relay neuron-connecting neuron and it transmit the signal from sensory neuron to motor neuron.
  4. Motor neuron- carries the signal or response from spinal cord to the receptor organ.

EXAMPLES of reflex action-

  1. Pulled back of hand from the flame
  2. Watering of mouth by reflex when we are hungry
  3. Sudden close of eye when an abject reaches your eye.
  4. Removal of your hand from sharp object.
  5. Change in Size of pupil in reflex to light.



  • Brain is the main coordinating centre of the body.
  • The brain and spinal cord constitute the central nervous system.
  • They receive information from all parts of the body and integrate it.
Central nervous system(CNS) Peripheral nervous system(PNS)
It include brain and spinal cord It includes all the nerves associated with CNS
It is site of information processing and control They help in communication between CNS and other part of body





  • it is main thinking part of brain
  • Fore brain consist of cerebrum, thalamus, and hypothalamus
  • It has regions which receive sensory impulses from various receptors.
  • Association area in the brain is responsible for complex functions like memory, communication and interpreting the sensory information with the information from other receptor as well as with information already stored in brain.
  • Fore brain control body temperature, urge of eating and drinking etc.


  • Many involuntary actions are controlled by mid brain and hind brain.
  • Example-it control reflex movement of head, neck, and trunk in response to visual and auditory stimuli.
  • It controls the reflex movements of the eye muscles, changes in pupil size and shape of the eye lens.
  • Mid brain and hind brain form the brain stem.


  • it consists of Pons, cerebellum and medulla oblongata.
  • Hind brain control number of involuntary actions like-
  • Blood pressure, salivation, vomiting, respiration they are mainly regulated by medulla
  • Balance of body, speech and muscular activity are mainly regulated by cerebellum.



  • Plants have neither nervous system nor muscles.
  • So plants hormones and electro-chemical communication play a major role in their coordination.
  • Plants show two different types of movements- one dependent on the growth and other independent of growth.
  • Growth independent type of movement (nastic movement) include electrical-chemical means of communication from cell to cell, in response to stimulus plant cells change shape by changing in the amount of water in them, resulting in swelling or shrinking.


Example- shrinking of leaves when touching the sensitive plant like shame plant (mimosa pudica).


  • Movement due to growth( tropic movement) includes various type of plant movement in response to environmental triggers such as light, gravity, water etc. These directional movements (tropic) can be either towards the stimulus, or away from it.
  1. POSITIVE GEOTROPIC– movement of plant part toward the gravity. Example – roots
  2. NEGATIVE GEOTROPIC– movement of plant part against the direction of gravity. Examples-stem


  1. POSITIVE PHOTOTROPIC – movement of plant part towards the direction of light. Example-sunflower
  2. NEGATIVE PHOTOTROPIC– movement of plant part against the direction of light. Example-roots


CHEMOTROPISM- movement of plant part navigated by chemical stimulus. Example- growth of pollen tubes towards ovules.


HYDROTROPISM movement of plant part towards or away the moisture.


If movement is towards the moisture it is known as positive hydrotropism and if movement is away the moisture it is known as negative hydrotropism.


  • HORMONES are the chemical compounds synthesized and released by plants all around the original cells.
  • If the surrounding cells have the means to detect this chemical compound, then they would be able to recognize information, and even transmit it.
  • This is slower method of coordination, but it can potentially reach all the cell of the body.
  • Plant hormones help to coordinate growth, development and responses to environment.



  • Sunlight stimulates the synthesis of auxin at the shoot tip.
  • Auxin helps in growth of stem.
  • Auxin concentrated at the shady part of shoot and stimulates cell growth in this region and cause bending of tip towards light.
  • Auxin promotes flowering ex in pineapple
  • Auxins are widely used as herbicides.


  • It promotes stem growth.
  • It elongates and improves the shape of apple
  • It promotes early seed production
  • It delays senescence (plant aging).


  • IT promotes cell division.
  • They are present in greater concentration in areas of rapid cell division such as fruits and seeds.
  • It helps to produce new leaves.
  • It delays leaf senescence.


  • IT inhibits the plant growth.
  • It promotes wilting of leaves.
  • It is also known as stress hormone.
  • It stimulates the closure of stomata to increase the tolerance of plants in stress conditions.


  • It promotes ripening of and growth of fruits.
  • It promotes yellowing and senescence of leaves.
  • It helps in breaking the dormancy in buds and seeds.
  • It stimulates the formation of separation layer in leaves, flowers and fruits.


  • HORMONES are chemical compound produced by endocrine gland and released into the blood and transported to different target organs.
  • The timing and amount of hormones released regulated by feedback mechanism of human body.
  • Release of hormones is regulated by hypothalamus.


GROWTH HORMONE It is secreted by pituitary. Regulate growth of bones and all organs. PITUITARY GLAND
PROLACTIN Synthesizing milk during pregnancy. PITUITARY GLAND

Gametes formation.

-It stimulates the follicle cells in the ovaries to develop into mature eggs.

-In male it stimulates secretion of male hormone, TESTOSTERONE. In females, it stimulates the secretion of OESTROGEN and PROGESTERONE.



It controls the growth and functioning of the THYROID GLAND.

Regulate metabolism of fat, protein and carbohydrate.

Maintain balanced growth of body.

INSULIN Reduce blood glucose level. PANCREAS
GLUCAGON Increases the blood glucose level. PANCREAS
ANDROGEN Regulate changes during puberty in males like facial hair growth, low pitch voice, TESTES
ESTROGEN AND PROGESTEREON Regulate changes during puberty in females such as growth of uterus, fallopian tube, growth of breasts etc. OVARIES


Both these hormones together control emotions, fear, anger, blood pressure, heart beat, respiration and relaxation of smooth muscles. ADRENAL MEDULLA
GLUCOCORTICOIDS Regulate the metabolism of protein, fat and carbohydrates in the body. ADRENAL CORTEX(KIDNEY)


Regulate minerals and water balance in the body ADRENAL CORTEX(KIDNEY)
MELANOTONIN Regulate sleep cycle( circadian rhythm) PINEAL GLAND




  1. Thyroid C) Pancreas
  2. Pituitary

ANSWER- A) thyroid gland releases thyroxin hormone. It regulates the metabolism and blood pressure of body.

B) Pituitary gland releases growth hormone. It helps the bones and all other body organs to grow properly.

C) Pancreas secreted insulin. It helps in maintaining blood glucose level.


ANSWER- Testis produces sperm and secreted testosterone hormone. Their important functions are as follows:

I) it stimulates sperm production

ii) It stimulate to develop secondary sexual characters in males like growth of facial hairs, low pitch voice etc.

iii) It stimulate the development, maturation and functioning of male accessory sex organs like vas deferens and seminal vesicles.






ANSWER- I) auxin and gibberellins

ii) Cytokinin

iii) abscisic acid

iv) abscisic acid


ANSWER- abscisic acid is plant hormone which inhibits the plant growth. Its other functions include

I) it promotes the dormancy in seeds and buds.

ii) It promotes closing of stomata.


ANSWER- i) endocrine system releases the hormones in blood.

ii) Timing and quantity of hormone secretion is regulated by feedback mechanism of body.

iii) The working of endocrine gland is controlled by nervous system. The hormones produced by the endocrine system act as messengers between the nervous system and the organs of the body.



ANSWER- a) main function of nervous system are-

  • Coordinates the different activities of the body
  • Help all other system of body to work together.
  • The nervous system of all the animals is composed of specialized cells called neurons which can detect, receive and transmit different kind of stimulus.

b) The movement of any part of plant body is due to change in shape of plant cells.

Plant maintains their coordination by electro-chemical communication and by plant hormones.

Plant hormones help in growth, development and response to environment stimuli.


Class 10th Class 6th Class 7th Geography

Structure and Interior of the Earth NCERT Notes on Geography

Interior of the Earth


Earths Structure
  • The internal structure of the earth is layered.
  • The Earth is generally divided into four major layers: the crust, mantle, inner core, and outer core.
  • Earth’s crust is the outermost layer composed of various types of rocks.
  • Below the crust lies the Lithosphere
  • These lithospheric plates appear to “float” and move around on the more ductile asthenosphere
  • The boundary between the crust and mantle is generally called the Mohorovičić discontinuity
  • The continental crust is thicker in comparison to oceanic crust.
  • The lithosphere is the upper 80 Kilometers layer composed of both the crust and part of the upper mantle
  • Earth’s mantle is a rocky shell about 2,890 Kms thick that constitutes about 84 percent of Earth’s volume.
  • The outer core is in the liquid state.
  • The inner core is in solid-state.

Earth’s Crust-

  • There are two types of earth’s crust
Oceanic Crust Continental Crust
  • The oceanic crust is thinner
  • It is composed of basalt
  • It has a high density
  • The continental crust is thicker
  • It is composed of Granite
  • It has low density
  • The low density helps it to flow over the oceanic crust


Earth’s Mantle

  • Earth’s mantle has olivine rock.
  • The temperatures increase with depths.
  • The temperature is lowest near the crust and increases with depth.
  • The highest temperatures are found near the mantle material as it is in contact with the heat-producing core.
  • This steady increase of temperature with depth is known as the geothermal gradient.
  • This temperature difference responsible for different rock behaviors, and the different rock behaviors are used to divide the mantle into two different zones.
  • Rocks in the upper mantle are cool and brittle, while rocks in the lower mantle are hot and soft (but not molten).
  • Rocks in the upper mantle are brittle enough to break under stress and produce earthquakes.
  • However, rocks in the lower mantle are soft and flow when subjected to forces instead of breaking.
  • The lower limit of brittle behavior is the boundary between the upper and lower mantle.

Earth’s Core

  • It is composed of alloys of iron and nickel
  • the core gives heat to the inside of earth
  • the radioactive material which is present inside it release heat as they break down into more stable substances.
  • The core is divided into two different zones.
  • The outer core is a liquid because the high temperatures melt the iron-nickel alloy.
  • The inner core is a solid even though its temperature is higher than the outer core because of very high pressure from the weight of rocks lying above it .

Mineral and Energy Resources : NCERT Geography Lesson For class 10th

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Electromagnetic Waves ,Wavelength and Frequency Explained

Wave Length – The Minimum Distance in which a wave repeats itself is called its wavelength

  • At the time Maxwell predicted the existence of electromagnetic waves, the
    only familiar electromagnetic waves were the visible light waves.
  • The existence of ultraviolet and infrared waves was barely established.
  • By the end of the nineteenth century, X-rays and gamma rays had also been discovered.
  • electromagnetic waves include visible light waves, X-rays, gamma rays, radio waves, microwaves, ultraviolet and infrared waves.
  • The classification of em waves according to frequency is the electromagnetic
  • There is no sharp division between one kind of wave and the next.
  • The classification is based roughly on how the waves are produced and/or detected.

Sound Free Lesson For Class 9th NCERT

Speed=Frequency ❌Wavelength.

  • Remember More the wavelength less the frequency and vice versa.
  • also try to remember the wavelength and the frequency can be found out

Tricks to remember the Wavelength series of  Electromagnetic Waves 

  • R-Roman Radio
  • M-Men    Microwave
  • I-Invented Infrared
  • U-Unusual Ultra Violet
  • X-ray-       X-ray
  • G-Guns   Gamma Rays
  • The Visible rays is in Between infrared and Ultra Violet

Roman men invented unusual x-ray guns.

Class 10th Science

Heredity Evolution,Speciation Notes on Science For Class 10th

Sex determination in human beings

  • Human beings have 23 pairs of chromosomes in the nucleus of the cell.
  • Out of this two chromosomes are sex chromosomes X and Y.
  • The female has two X chromosomes (XX) and male has one X and one Y
    chromosome (XY).
  • The sperms and eggs have one set of sex chromosomes.
  • Some sperms have X chromosome and some have Y chromosome.
  • All eggs have X chromosome.
  • If a sperm having X chromosome fuses with an egg having X chromosome the child will be a girl.
  • If a sperm having Y chromosome fuses with an egg having X chromosome the child will be a boy.

Variation and Evolution influence Survival Positively or Negatively

a) Some variations may help organisms to survive :-

  • There are some beetles living in green bushes.
  • They increase their numbers by reproduction.
  • Crows can easily see the red beetles and they are eaten by the crows.
  • During reproduction due to some variation some green beetles are produced instead of red beetles.
  • The green beetles are not visible to crows and are not eaten by them.
  • Then gradually the population of the red beetles decreases and the
    population of the green beetles increases.
  • This variation has helped the organisms to survive.

b) Some variations do not help organisms to survive :-

  •  During sexual reproduction a colour variation occurs in red beetles and some blue beetles are produced instead of red beetles.
  • Both the red and blue beetles are visible to crows and are eaten by them.
  • Then the population of both red and blue beetles decreases.
  • This variation has not helped the organisms to survive

Aquired Traits and Inherited Traits

Distinguish between acquired and inherited traits giving one example of each

Acquired traits Inherited traits
A trait (or characteristic) of a organism
which is not inherited‘ but develops in
response to the environment is called an
acquired trait.
A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait.
The acquired traits of an organism can
not be passed on to its future generations.
he inherited traits of an organism are passed on to its future generations
e.g. low weight‘ of beetle, cut tail of a
e.g. red colour of beetles,
fur coat of guinea pigs.

Aquired traits cannot be passed from one generation to the next :-

  •  If the population of beetles increases and plants are affected by diseases, then the food available for the beetles decreases and their body weight also decreases.
  • If after a few years the availability of food increases then the body weight of the beetles also increases.
  • This acquired trait cannot be passed from one generation to the next because there is no change in their genetic composition.

Speciation  and factors Influencing Speciation

  • Formation of new species from existing species is called speciation
  • The formation of new species from existing species is mainly due to one or more of the following factors.
  • They are :- Accumulation of variations, Physical barriers, Genetic drift, Natural selection and migration.
  1.  Accumulation of variations :- The differences between the individuals of the same species is called variations. The accumulation of variations over several generations produce new species.
  2. Physical barriers :- Populations may get separated by physical barriers like mountains, rivers, lakes etc. These isolated groups produce variations which can produce new species.
  3. Genetic drift :- Natural calamities or introduction of new members of the same species in an area can produce changes in the gene pool of the population and new variations are produced which can produce new species.
  4. Natural selection :- Only those individuals of a species which have useful variations and can adapt to the changes in the environment survive and the others die. These organisms can produce variations and new species.
  5. Migration :- Some individuals of a species may migrate to a new geographical area and adjust to the changes in the environment there and develop new variations and produce new species.


  • The gradual changes taking place in living organisms giving rise to new organisms due to changes in their genetic composition is called evolution.

Evidences of evolution

  • There are a number of common features in different organisms which provide evidence to show evolutionary relationship.
  • The main evidences of evolution are from the study of :- Homologous organs, Analogous organs and Fossils.

a) Homologous organs :- are organs which are similar in structure but different in functions.
Eg :- The fore limbs of amphibians, reptiles, birds, and mammals have similar structures but different functions.

Frog (amphibian) uses its fore limb to raise the front of the body. Lizard (reptile) uses its fore limb for walking and running. Birds fore limbs are modified as wings for flying.
Mammals use the fore limbs for grasping, walking, running, swimming,flying etc.

b) Analogous organs :- are organs which are different in structures but similar in functions.
Eg :- The wings of butterfly, bird and bat have different structures but similar functions. This shows evolutionary relationship.

Evolution by stages :-

  • Complex organisms and its organs developed from simpler organisms gradually over generations.
  • Evolution of eyes :- The eyes of planaria are just eye spots to detect light. It developed gradually into a complex organ in higher animals.
  • Evolution of feathers :- Feathers were first developed in dinosaurs and used for protection from cold. Later birds used them for flying.
  • Evolution by artificial selection :- Humans cultivated wild cabbage for over 2000 years and produced different vegetables from it by artificial selection.
    Eg :- Cabbage – by selecting short distance between the leaves.
    Cauliflower – by selecting sterile flowers.
    Kale – by selecting large leaves
    Kholrabi – by selecting the swollen stem
    Broccoli – by arresting flower growth

Evolution should not be equated with progress :-

  • Evolution has not resulted in progress.
  • Evolution has resulted in the formation of several complex species from simpler species due to variations, genetic drift and natural selection.
  • This does not mean that one species gets eliminated when new species are formed or that the new species are better than the older species.
  • Species get eliminated only if they are not able to adapt to the changes in the environment.
  • Several species which could adapt to the changes in the environment still continue to survive for example bacteria.
  • Human beings have not evolved from chimpanzees.
  • They had a common ancestor from which they evolved separately.
  • Human beings are not the pinnacle of evolution but they are only one species among the several evolving species.

Human evolution :- (Homo sapiens)

  • There is a great diversity among human beings in their form and features around the world.
  • Human beings evolved in Africa.
  • Some of them stayed there and others migrated to different parts of the world.
  • Then due to genetic variations and the environmental changes in different geographical regions they developed changes in their forms and features.

Heredity And Evolution : Class 10 Notes on NCERT

Heredity and Evolution NCERT Solutions For Class 10th SCIENCE

Class 10th Science

Heredity And Evolution : Class 10 Notes on NCERT


  • Heredity :- The process of transfer of characters or traits from the parents to their offsprings is called heredity.
  • Variations :- The differences between the characters or traits among the individuals of the same species are called variations.
  • For example human height is a trait which shows different variations like tall, short, medium etc.

  • Another example is earlobe, it shows two variations free earlobe and attached earlobe.
  • The variation is necessary for evolution The great advantage of variation is that it increases the chance of survival in a changing environment

Accumulation of variations during reproduction

  • The reproduction produces variations in offsprings .
  • The  minor variations are seen  due to inaccuracies in DNA copying.
  • These variations are less in asexual reproduction and more in sexual reproduction.
  • Some variations are useful variations and they help the organism to adjust to the changes in the environment.
  • Some variations do not help the organism to adjust to the changes in the environment and they may die and become extinct

Transfer of characters

  • Characters are transferred through DNA molecules present in the gene on the chromosomes which are present in the nucleus of the cell.
  • The inheritance of characters is due to the fact that both the father and mother contributes equal amount of genetic material to the child.
  • So for each trait there are two factors one from the father and one from the mother
The structure of the chromosome

CHROMOSOME: A thread like structure in the nucleus of cell formed of DNA and protein
which carries the genes.
GENE: A unit of DNA or a segment of DNA which controls specific characteristic of an
ALLELES: They are various forms of a gene which occur at the same particular position or
locus over the chromosomes.
DOMINANT GENE: The gene which decide the expression of a character even in the presence of an alternative gene.
RECESSIVE GENE: The gene which decides the expression of an organism in the presence of another identical gene.

  • The dominant gene is represented by a capital letter and the corresponding recessive gene is represented by the same letter in small.
  • For example the dominant gene for tallness is represented by T and the recessive gene for dwarfness is represented by t.
  • Genotype:-  The genotype is the description of genes present in an organism.
  • Phenotype:- The characteristic or trait which is visible in an organism Is called phenotype. Ex- Tall or dwarf.

Rules for the Inheritance of Traits – Mendel’s Contributions

Mono-Hybrid Crossing 

  • Gregor Johann Mendel conducted experiments with garden pea plants and determined the rules for the inheritance of traits
  • Mendel selected pea plants having one pair of character – a tall pea plant and a
    short pea plant.
  • He selected pure tall (TT) and pure short (tt) pea plants and cross pollinated them.
  • He obtained all tall plants (Tt) in the first generation (F1 )
  • When the first generation plants were self pollinated, he obtained tall and dwarf
    plants in the ratio 3:1 in the second generation. (F2)
  • The ratio of pure tall (TT), hybrid tall (Tt) and pure dwarf (tt) was in the ratio 1:2:1
  • The trait that is expressed in the F1 generation is called the dominant trait and the trait that is suppressed in the F1 is called the recessive trait.

Dihybrid cross

  • When plants having two pairs of characters (Eg:- shape and colour of seeds) were crossed (Dihybrid cross)
  • Mendel selected pea plants having two pairs of characters – shape and colour
    of seed.
  • He selected plants having round yellow seeds (RRYY) and wrinkled green seeds (rryy) and cross pollinated them.
  • He obtained all plants with round yellow seeds (RrYy) in the F1 generation.
  • When these plants were self pollinated in the F2 generation out of 16 plants, 9 had round yellow (RrYy), 3 had round green (Rryy), 3 had wrinkled yellow (rrYy) and 1 had wrinkled green (rryy) seed  In the ratio 9:3:3:1.Heredity and Evolution NCERT Solutions For Class 10th SCIENCE
Class 10th Science

Sexual Reproduction in Human Beings : Study Notes for Class 10th Science

Reproduction in human beings

  • Puberty-it is the period during which adolescents reach sexual maturity and become capable of reproduction
  • During early teenage whole new set of changes occurs, appearance of body and proportions change and new features develop.
  • As the rate of general body growth slows down reproductive tissues begin to mature.
  • If animals are to participate in the process of mating, their state of sexual maturity must be identifiable by other individuals.
Pubertal changes in males Pubertal changes in females
a) deepening of voice(low pitch)
b) broadening of shoulders
c) appearance of beard & moustaches
d) Growth of axillary & pubic hairs
a) high pitch voice
b) widening of hips
c) Growth of axillary & pubic hairs
d) Initiation of menstruation
e) Growth of mammary glands.

Male reproductive system

Male reproductive system
Male reproductive system

1. Testis:

  • Testis is a galndular organ made up of fine tubules.
  • The formation of germ cells take place in testes, located outside the abdominal cavity in scrotum because sperm formation requires a lower body temperature.
  • testis also produces certain hormones, like tetosterone which are responsible for secondary sexual characters in humans.
  • These are deep male voice, hair growth in pubic area and under armpits, and facial hair.

2. Seminal Vesicle: Once sperm is produced it is stored in seminal vesicle.

3. Vas Deferens:

  • Vas deference is the tube through which semen containing sperm is transferred out.
  • The sperms produced are transferred by vas deferens which unites with a tube coming from urinary bladder.
  • Urethra forms a common passage for both sperm and urine.
  • To make the transportation of sperms easier prostate and seminal vesicles add their seceretions along the path of vas deferens, that makes the sperms to be transported in fluid which provides nutrition.
  • Cowper‘s gland – Produces white viscous & alkaline secretion
  • Semen = sperm& secretion of accessory glands

Female Reproductive system

1. Ovary:

  • Ovaries are situated on left and right side of the uterus.
  • The female germ-cells are produced in ovary, which is also responsible for production of oestrogen.
  • On reaching puberty some of the immature eggs present in the ovary of a girl start maturing.

2. Fallopian Tubes:

  • Fallopian tubes extends on both sides of the uterus in transverse direction.
  • Fallopian tubes have finger like structures which catch the eggs to transfer them to the uterus.

3. Uterus:

  • Uterus is a bag like structure, with an opening in the vagina.
  • Uterus opens into the vagina through cervix.

Fertilization In Human Beings 

  • Sperms enter through the vaginal passage during sexual intercourse and encounters egg in fallopian tube.
  • Once eggs reach uterus, a layer of soft tissues develops to support the embryo.
  • This layer is called corpus luteum.
  • If fertilization takes place, then the embryo develops into a foetus and ultimately to a fully developed child over a period of about 9 months
  • The zygote gets implanted into the lining of the uterus and starts dividing.
  • The uterus prepares itself every month to receive and nurture the the embryo, the lining thickens and is richly supplied with blood to nourish the growing embryo.
  • The embryo gets nutrition from the mother’s blood with the help of a tissue called placenta, a disc embedded in uterine wall.
  • The child is born as a result of rhythmic contractions of the muscles of uterus.
Female reproductive system
Female reproductive system
  • Implantation : Attachment of embryo to the lining of uterus.
  • Placenta : A connection between the mother & the foetus
  • The foetus meets all its developmental needs such as nutrition, respiration and excretion through the placenta.
  • Gestation period :The period between fertilisation & birth

Menstrual Cycle in Females:

  • If no fertilization takes place then after about two weeks the dead eggs and corpus luteum gets expelled out of the uterus through vagina.
  • This process takes place over a period of about three to four days.
  • This clears the way for new batch of eggs to come in the uterus.
  • The whole cycle from egg production to the expulsion of eggs takes about four weeks.
  • This cycle is known as Menstrual Cycle.
  • Apart from humans, some primates like Chimpanzee and Gorilla also show same
  • Ovary secretes one of the important hormones estrogen, which is responsible for secondary sexual characters in female, like thin voice and breast enlargement.

Menarche – commencement of menstrual cycle at puberty which marks the beginning of reproductive life of the human female.

Menopause – cessation of menstrual cycle which marks the end of the  reproductive life of a human female.

Reproductive Health and Birth Control Methods 

  • Creation of a mechanical barrier is a method of contraceptive so that the sperm does not reach the egg is called condoms.
  • Oral pills change the hormonal balance of the body
  • Loops and copper-T is placed in the uterus to prevent pregnancy
  • Surgical method can be used to block vas deferens in male and fallopian tube in female.

Read Here on Sexual Reproduction In Plants(Second Part of the Lesson) 

Previously Asked Questions on Reproduction in Human beings 

  1. How does the male gamete reach the egg present in the ovary?
    The pollen tube releases the male gametes in the embryo sac .
  2. What are gonads?
    Gonads are the primary sex organs which produce gametes & secrete sex
  3.  Define syngamy.
    The process of fusion of male gamete with the female gamete is known as syngamy.
  4.  At what age human males attain puberty?
    At the age of 12-14 years
  5.  At what age human females attain puberty?
    At the age of 10-12 years.
  6.  What are the functions of gonads?
    i) production of gametes
    ii) secretion of sex hormones.
  7. Why are testes located outside the abdominal cavity ?
    Sperm formation requires a temperature lower than that of the normal body temperature.
  8.  Where are ovaries located in human females?
    Ovaries are present in the abdominal cavity near the kidneys.
  9. What is placenta?
    A connection between the mother & the foetus.The foetus meets it all its developmental needs such as nutrition, respiration and excretion through the placenta.
  10. What is menstruation?
    If fertilization does not occur the uterine wall slowly breaks & comes out through vagina as blood and mucous.
  11. What is ovulation?
    It is the process of release of a mature ovum from the ovary.