Light and Optics
A complete physics website covering light, reflection, refraction, mirrors, lenses, optical instruments, human eye, dispersion, total internal reflection, formulas, diagrams, solved examples, and exercises.
1. Nature of Light
Light is a form of energy that enables us to see objects.
Source of Light
→
Light Rays
→
Vision
Properties of Light
- Travels in straight line
- Can reflect and refract
- Has very high speed
Speed of light = 3 × 10⁸ m/s
2. Reflection of Light
The bouncing back of light from a surface is called reflection.
∠i = ∠r
3. Refraction of Light
The bending of light when it passes from one medium to another is called refraction.
n = sin i / sin r
4. Spherical Mirrors
Types of Mirrors
| Mirror | Nature |
|---|---|
| Concave Mirror | Converging mirror |
| Convex Mirror | Diverging mirror |
1/f = 1/v + 1/u
5. Lenses
Types of Lenses
- Convex Lens
- Concave Lens
Power of lens = 1/f
P = 1/f
6. Human Eye
The human eye acts like a camera and forms image on retina.
Defects of Vision
- Myopia
- Hypermetropia
- Astigmatism
7. Dispersion of Light
The splitting of white light into seven colors is called dispersion.
8. Practice Exercises
Short Questions
- Define reflection.
- State laws of reflection.
- Define refraction.
- What is dispersion?
- Name defects of vision.
Numerical Problems
- Find power of lens if focal length is 0.5 m.
- Find refractive index if sin i = 0.8 and sin r = 0.5.
- Calculate focal length if power is 2 D.
9. Formula Summary
| Topic | Formula |
|---|---|
| Reflection | ∠i = ∠r |
| Refraction | n = sin i / sin r |
| Mirror Formula | 1/f = 1/v + 1/u |
| Lens Power | P = 1/f |