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A small round mirror on a bike shows the whole road. This track says how.

This track is Light – Reflection and Refraction. It is Chapter 9 of your Class 10 Science book. Two rules say where light goes. Two formulas turn the rules into numbers.

What this track covers

• Bouncing by the rule: the two laws of reflection.
• Mirrors that are not flat: pole, centre, focus and f = R/2.
• What the mirror does to an image: place decides the image.
• Two rays are enough: draw two rays and find the image.
• The mirror formula: one line, with signs.
• Bending by a rule too: refraction (light bending), and the refractive index.
• The lens formula: the same idea for a lens.
• How strong a lens is: power, in dioptres.
• Through a glass slab: the ray leaves parallel, shifted sideways.

Quick catch-up

None of this is required. Read a line only if it feels shaky.

• Light bounces off a smooth surface.
• A flat mirror makes an image behind the mirror.
• Light bends where it crosses into another material.
• A lens is shaped glass that bends light.

One rule before anything else

Every lab here is a drawing on a screen. Never look at the Sun, even through a lens or mirror.