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Your eye works like a camera. A lens at the front. A screen at the back. The picture forms on the screen.

This is Chapter 10, in your NCERT Science book. It is called The Human Eye and the Colourful World. It uses the lens rules you already know.

What you will learn

• The eye is a lens, with a screen at the back.
• Focusing near and far. The lens changes shape.
• When far things blur. A concave lens fixes it.
• When near things blur. A convex lens fixes it.
• The eye with age. The near point moves away. A convex or bifocal lens helps.
• Light comes apart. A prism spreads white light into seven colours.
• Why the sky is blue. Air scatters blue light more than red.
• Why the Sun is red at the edge of the day. This means sunrise and sunset.

One safety rule, for every lesson

Never look at the Sun. Not with your eyes alone. Not through a lens, a prism or a mirror. Every lens and prism here is only a drawing. To see sky colours, look at clouds and walls. Never look at the Sun.

Need a quick recap?

These two lessons can help if you want a refresher.

• How strong a lens is: a lens's power, in dioptres.
• What a lens makes: two rays crossing to form a picture.