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

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.