Class 10 Science Light Reflection and Refraction Notes

Class 10 Science Light Reflection and Refraction Notes

Introduction

  • Light is a form of energy that enables us to see objects.
  • The study of light involves its behavior when it strikes surfaces (reflection) or passes through different mediums (refraction).

1. Reflection of Light

  • Definition: Bouncing back of light after striking a surface.
  • Laws of Reflection:
    1. The angle of incidence (i) is always equal to the angle of reflection (r).
    2. The incident ray, reflected ray, and normal all lie in the same plane.

Types of Reflection

  1. Regular Reflection: Reflection from smooth surfaces (e.g., mirrors).
  2. Diffused Reflection: Reflection from rough surfaces (e.g., paper, wall).

2. Refraction of Light

  • Definition: Bending of light when it passes from one medium to another (e.g., air to water).
  • Laws of Refraction:
    1. The incident ray, refracted ray, and normal all lie in the same plane.
    2. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.
    • Snell’s Law: sin⁡isin⁡r=constant\frac{\sin i}{\sin r} = \text{constant}sinrsini​=constant (refractive index)

Refractive Index

  • Definition: A measure of how much a medium can bend the light.
    • Refractive Index=sin⁡isin⁡r\text{Refractive Index} = \frac{\sin i}{\sin r}Refractive Index=sinrsini​

3. Images Formed by Mirrors

  • Concave Mirror (Converging Mirror): Curved inward, forms real or virtual images depending on object distance.
  • Convex Mirror (Diverging Mirror): Curved outward, always forms virtual, diminished images.

Mirror Formula:

1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1​=v1​+u1​
Where:

  • fff = focal length
  • vvv = image distance
  • uuu = object distance

4. Images Formed by Lenses

  • Concave Lens (Diverging Lens): Always forms a virtual, diminished image.
  • Convex Lens (Converging Lens): Can form real or virtual images depending on object position.

Lens Formula:

1f=1v−1u\frac{1}{f} = \frac{1}{v} – \frac{1}{u}f1​=v1​−u1​
Where:

  • fff = focal length
  • vvv = image distance
  • uuu = object distance

5. Refraction Through a Prism

  • When light passes through a prism, it bends and disperses into different colors (forming a spectrum).
  • Colors of the Spectrum (VIBGYOR):
    • Violet, Indigo, Blue, Green, Yellow, Orange, Red
  • Dispersion of Light: Separation of light into its component colors.

6. Applications of Reflection and Refraction

  1. Reflection:
    • Mirrors for personal grooming, vehicles
    • Periscopes in submarines
  2. Refraction:
    • Lenses in spectacles, microscopes, and telescopes
    • Optical fibers for communication