Table of Contents
Table of Contents
- Example of Refraction: Pencil in a Glass of Water
- Example of Refraction: Pencil in a Glass of Water and Oil
- Example of Refraction: Coin in a Container
- Summary
- What’s Next?
In the previous segment, we understood How light changes its direction due to change in its speed. In this segment, let’s look at some examples of refraction.
Example of refraction: Pencil in a glass of water
- Consider a pencil kept in a glass half-filled with water.
Pencil immersed in water
- To an observer, it appears that the pencil is broken at the interface of air and water.
- This is because light from the pencil undergoes refraction.
- Water is optically denser than air. So, when the light from the pencil travels from water to the air, through the glass, it undergoes refraction twice: when light travels from water to glass and when light travels from glass to air. However, as the glass is thin
compared to the other media, the light is considered to travel from water to air and thus it undergoes refraction only once.
- When light from the pencil undergoes refraction while travelling from water to air, the refracted light reaches the observer’s eyes. These refracted rays of light when traced backwards, converge at a position different to that of the original position of the pencil. This is where the image of the pencil is formed.
- Hence, the pencil appears broken as the image is formed at a different position than the pencil.
Example of refraction: Pencil in a glass of water and oil
- Optical density is the extent to which a medium bends light, whereas physical density is the ratio of the mass of an object to its volume.
- A medium with less physical density can be more optically dense and vice versa.
- An optically dense medium can bend light away from the normal to a greater extent than an optically rare medium.
- In the case of water and oil, the physical density of oil is less as compared to that of water. Hence, oil floats on water.
- At the same time, the optical density of water is less as compared to that of oil. Hence, oil can bend light to a greater degree.
- Consider a pencil kept in a glass half-filled with water. Add some oil to it.
