 # AP Class 10 Physical Science Chapter 3 Reflection of Light By Different Sources

Bouncing back of a light ray after hitting any surface is known as reflection. In our previous classes, we have learnt the laws of reflection which state that

• The angle of reflection is equal to the angle of incidence
• The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

In the Andhra Board Class 10 Science Chapter 3 Reflection of Light By Different Surfaces, students learn about the reflection of light in detail.

## Fermat principle

Light chooses the path that takes the least amount of time to travel. This is statement is also applicable to the reflection of light.

### Mirror Formula

The mirror formula is given as

$$\begin{array}{l}\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\end{array}$$

Following are the sign conventions that are to be followed for the mirror equation

• All distances must be measured from the pole.
• The distances measured in the direction of incident light must be considered positive and those measured in the direction opposite to the incident light must be considered negative.
• The height of the object and height of the image should be considered positive if measured upwards from the axis and negative if measured downwards.

Let us answer some chapter questions to better understand the concepts discussed in the chapter.

## Reflection of Light By Different Surfaces Chapter 3 Questions

1. State the laws of reflection of light.

The laws of reflection of the light state that:

• The incident ray, the reflected ray and the normal to the reflecting interface at the point of incidence all lie in the same plane.
• The angle of incidence equals the angle of reflection.
1. Why do we prefer a convex mirror as a rear-view mirror in the vehicles?