NIOS Class 10 Science Activity 15.4 Light Energy

In this activity, we will study how a light ray bends when it passes from air into a glass slab and again from glass back to air.

 

Light Energy Activity

This activity is based on the NIOS Class 10 science and technology (212) Chapter 15- Light Energy, Module 4.

Refraction of Light through a Glass Slab

Aim

To observe the refraction of light through a glass slab

Material Required

   1. Rectangular glass slab

   2. White drawing sheet

   3. Wooden drawing board

   4. Drawing pins

   5. Scale and pencil

Procedure

We place a rectangular glass slab on a white drawing sheet fixed on a wooden board and mark its boundary with a pencil.

We draw a straight line OC on the sheet obliquely with the boundary and fix two pins A and B along the line to represent the incident ray.

Now we look through the slab from the opposite side and fix another pin E so that pins A, B, and E appear in a straight line. After that, we fix pin F in line with A, ,B and E.

We remove the slab, pins, and join points E and F to meet the boundary at D, which is an emergent ray. The line AB represents the incident ray, CD the refracted ray, and EF the emergent ray. We also draw normal N₁CN₂ at C and N₃DN₄ at point D.

 

Observation

We observe that

1) The ray of light bends towards the normal when entering the glass slab (from air to glass)

2) The ray of light bends away from the normal when emerging from the glass slab (from glass to air).

3) The emergent ray EF is parallel to the incident ray AB but shifted sideways, showing lateral displacement.

Explanation

 When light travels from a rarer medium (air) to a denser medium (glass), it slows down and bends towards the normal.

When light travels from a denser medium to a rarer medium, it speeds up and bends away from the normal.

Conclusion

We can conclude that

   1.  Light deviates from its original path when it travels from one transparent medium to another transparent medium. This is called refraction of light.

    2. Incident ray and emergent ray are parallel to each other, which is lateral displacement.

    3. The amount of deviation (bending) depends on the angle of incidence and the refractive index of the medium.

 

 

Frequently Asked Questions

   1. What is the aim of activity 15.4?

 Answer – To study the refraction of light through a glass slab.

   2. What happened to the ray of light when it entered the glass slab from the air?

Answer – A Ray of light bends towards the normal because its speed slows down.

   3. What happens when the light ray emerges from the glass slab into the air?

Answer – The light ray bends away from the normal because its speed increases.

    4. What is refraction?

Answer – The deviation of a light ray from its original path when it travels from one medium to another.

   5. Why does refraction occur?

Answer – Refraction occurs because light travels at a different speed in different media.