Mirrors and Lenses

Overview

Light travels in straight lines and can be reflected by mirrors and bent (refracted) by lenses. This chapter studies how mirrors and lenses form images and where they are used.

Key concepts

• Light travels in a straight line.
• Reflection: light bouncing back from a surface like a mirror.
• A plane mirror forms an erect, same-size, laterally inverted image.
• Concave and convex mirrors form different kinds of images.
• Lenses refract light; convex lenses converge and concave lenses diverge it.

Important terms / formulae

• Reflection: bouncing of light from a surface.
• Refraction: bending of light passing into another medium.
• Lateral inversion: left-right reversal in a plane mirror.
• Laws of reflection: angle of incidence equals angle of reflection.

Solved example or key process

When you stand in front of a plane mirror and raise your right hand, the image appears to raise its left hand. This left-right reversal is called lateral inversion, and the image formed is erect and of the same size as you.

Important questions

1. State the laws of reflection of light.
2. Describe the image formed by a plane mirror.
3. Differentiate between a convex and a concave lens.
4. Give one use each of a concave mirror and a convex mirror.

Quick revision

Light travels straight, reflects off mirrors, and refracts through lenses. A plane mirror gives an erect, same-size, laterally inverted image. Convex lenses converge light; concave lenses diverge it.