Final answer:
When a thermometer is placed in a glass of water, the light rays refract as they pass through the water and glass, causing the thermometer reading to appear distorted. This phenomenon is a result of the different refractive indexes of glass and water. A similar observation can be made with a broken pencil placed in water.
Step-by-step explanation:
In physics, when a thermometer is placed in a glass of water, the light rays from the thermometer refract as they pass through the water and glass. Refraction is the bending of light when it passes from one medium to another with a different refractive index. The refractive index of glass is 1.50 and the refractive index of water is 1.333.
As a result of refraction, the thermometer reading may appear distorted when viewed through a glass of water. This is because the glass and water have different refractive indexes, causing the light to change direction as it passes from the thermometer into the water and then into our eyes.
A similar observation can be made with a broken pencil placed in a glass of water. The pencil appears bent when viewed sideways through the water due to refraction.