Topic 7: One-Page Revision Sheet

Chapter 13: Refraction of Light – One Page Revision

1. Refraction of Light

Refraction is the phenomenon of change in direction of light when it passes from one transparent medium to another due to change in its speed.

2. Cause of Refraction

Refraction occurs because speed of light is different in different media.

3. Important Terms

• Incident ray
• Refracted ray
• Normal
• Angle of incidence (i)
• Angle of refraction (r)

4. Laws of Refraction (Snell’s Laws)

• Incident ray, refracted ray and normal lie in same plane
• sin i / sin r = constant

5. Refractive Index (μ)

Absolute refractive index:
μ = c / v

Relative refractive index:
μ₂₁ = v₁ / v₂

In terms of angles:
μ = sin i / sin r

6. Bending of Light

• Rarer → Denser medium: bends towards normal
• Denser → Rarer medium: bends away from normal

7. Refraction Through Glass Slab

• Emergent ray is parallel to incident ray
• Angle of emergence = Angle of incidence

8. Lateral Displacement

The perpendicular distance between incident ray and emergent ray.

Factors Affecting Lateral Displacement

• Thickness of slab
• Angle of incidence
• Refractive index of slab

9. Lenses

• Convex lens – converging
• Concave lens – diverging

10. Lens Formula

1/f = 1/v + 1/u

11. Magnification by Lens

m = v / u

12. Power of a Lens

P = 1 / f (f in metre)

• Convex lens → positive power
• Concave lens → negative power

13. Combination of Lenses

P = P₁ + P₂

14. Important CET Points

• Snell’s law numericals
• Refractive index formulas
• Lateral displacement concept
• Lens formula & magnification numericals
• Power of lens and sign convention