Class 10 Physics - Light: Reflection and Refraction

1. Reflection of Light

Reflection = When light bounces back from a surface.

Laws of Reflection:

1. Angle of incidence = Angle of reflection
2. Incident ray, reflected ray, and normal lie in the same plane

Types of Mirrors:

2. Mirror Formula

$$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$$

Where:

• f = Focal length
• v = Image distance
• u = Object distance

Sign Convention:

• All distances measured from pole
• Distances in direction of incident light = positive
• Distances against incident light = negative

3. Magnification

$$m = \frac{h'}{h} = -\frac{v}{u}$$

• m > 1 → Enlarged image
• m < 1 → Diminished image
• m = 1 → Same size

4. Refraction of Light

Refraction = Bending of light when it passes from one medium to another.

Laws of Refraction:

1. Incident ray, refracted ray, and normal lie in same plane
2. Snell's Law: n₁ sin i = n₂ sin r

Refractive Index:

$$n = \frac{c}{v} = \frac{\sin i}{\sin r}$$

5. Lens Formula

$$\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$$

Power of Lens:

$$P = \frac{1}{f}$$ (in metres)

Unit: Dioptre (D)

✔️ Important Formulas to Remember

1. Mirror Formula: 1/f = 1/v + 1/u
2. Lens Formula: 1/f = 1/v - 1/u
3. Magnification: m = -v/u = h'/h
4. Power: P = 1/f (D)

Good luck with your exams! 📚