## Refraction of The Light

Subject: Science

#### Overview

The bending of light as it passes from one transparent medium to another medium is called refraction of light. Refraction of the light note provides an information about Laws of refraction, definition of refraction with the example.
##### Refraction of The Light

An object that lets light pass through it is called a medium. Light does not need a medium to travel, unlike sound because it is capable of travelling through space. The bending of light as, it passes from one transparent medium to another medium, is called refraction of light. It occurs because light travels at the lower speed in an optically denser medium. It is due to refraction that a pencil appears bent when dipped obliquely in water.

#### Laws of refraction:

1. The incident ray, the normal and the refracted ray all lie in the same plane.
2. The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from the denser medium to the rarer medium.
3. If a ray of light travels normally ( i = 0), it goes straight.

The position and nature of the image formed by concave lens

 S.no. Position of object Position and nature of image formed 1. At infinity, Image is real, inverted, small size and forms at A. 2. Beyond C, Image is real, inverted and smaller size. Image is formed between F and C. 3. At C, Image is real, inverted and small in size. Image is formed at C. 4. Between F and C Image is real, inverted and magnified. Image is formed beyond C. 5. At F, Image is real, inverted and highly magnified. Image is formed at infinity. 6. Between pole, O and F Image is virtual, erect and magnified. Image is formed behind the mirror.

Activity

1. Place a clean sheet of white sheet on the table
2. Place a glass slab on the table.
3. Draw the outline of glass slab with the help of pencil in the paper. Name the outline ABCD.
4. As in the figure, place a pin at P and Q at the side of AB. P and Q should be 8 cm far.
5. Looking from the other side of the glass slab fix two pins R and S such that your eye and the feet of all the pins lie in one straight line.
6. Now remove glass slab and pins
7. Now join two point P and Q and stretch up to the X.
8. Join two point R and S and stretch up to the Y.
9. Join point X and Y.
10. Strech PQ up toZ.
11. Draw line MN from point X and M1M2from point Y.

Here, the ray from the air, PX is incident ray. Ray passing from glass slab XY is refracted ray. YS ray is emergent ray. XY is an actualpath of ray PQ, Here PX ray bends towards the normal. XY ray again bends away from M1M2. This experiment shows that ray bends when it travels from one medium to another.

##### Things to remember
• The bending of light as it passes from one transparent medium to another medium is called refraction of light.
• Laws of refraction:
1. The incident ray, the normal and the refracted ray all lie in the same plane
2. The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from denser medium to rarer medium.
3. If a ray of light travels normally (< i = 0), it goes straight.
• It includes every relationship which established among the people.
• There can be more than one community in a society. Community smaller than society.
• It is a network of social relationships which cannot see or touched.
• common interests and common objectives are not necessary for society.
##### Refraction Of Light Through a Glass Slab

The laws of refraction are:

• The incident ray, the normal and the refracted ray all lie in the same plane.
• The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from the denser medium to the rarer medium.
• If a ray of light travels normally ( i = 0), it goes straight.
Due to refraction of light, the light rays coming from the apparent position of the fish appears shorter eyes and he hits the spear at that point but the fish does not get hit because the actual position of the fish is slightly below that of apparent position of the fish.
The process of bending of light as it passes from one medium to another medium is called refraction of light.

AO → incident ray
OB → refracted ray
BC → emergent ray
MN and M'N' = normal
∠AOM = Angle of incidence
∠BON = Angle of refraction
The velocity of light in rarer medium is greater than velocity of the light in denser medium. So, because of the variation of speed of light in two medias, the light bends which is the main cause of refraction.
1. A stick partly immersed in water and placed inclined to the surface, appears bent at the surface.
2. A swimming pool appears shallower than it really is.
The laws of refraction are as follows:
1. The incident ray, refracted ray and the normal lies in the same point of a plane.
2. A ray of light bends towards the normal when it travels from rarer medium to denser medium and bends away from the normal when it travels from denser medium to rarer medium.
3. The ratio of sine of angle of incidence (Sin i) to the sine of angle of refraction (sin r) is always constant for a given pair of media.
Mathematically,
= µ (constant)
The constant quantity 'µ' is called refractive index.
The refractive index of a medium is defined as the ratio of velocity light in air (or vacuum) to the velocity of the light in the medium.
∴ RI of a medium =
1. The refraction of light is shown in the figure.
2. In the given figure:
AO → incident ray
OB → refracted ray
BC → emergent ray
MN = normal
∠AOM = Angle of incidence
∠BON = Angle of refraction
3. Since the refracted ray bends towards the normal, we can say light comes from the rarer medium (water) and falls to denser medium (glass).
1. The refraction of light is shown in the figure.
2. Due to refraction of light, the light ray coming from the parts of pipe inside the water gets bent at the surface of the water. These deviated rays appear on our eyes and the parts of ruler inside the water appear bent.