Light Reflection and Refraction | Class 10 Science - Physics

Light - Reflection and Refraction

Light is made up of electromagnetic waves which produce the sensation of vision in us. An electromagnetic wave is a wave made up of oscillating electric & magnetic fields. This electromagnetic wave oscillates in mutually perpendicular direction and also perpendicular to the path of propagation of the wave. According to Quantum Theory, light is transmitted as tiny bundles of energy called photons. The wavelength range of visible light = 4 x 10-7 m to 8 x 10-7 m. Speed of light = 3 x 108 m/s LIGHT IS MADE UP OF ELECTROMAGNETIC WAVES, Oscillating electric and magnetic fields, which oscillate in mutually perpendicular direction and also perpendicular to the path of propagation of the wave.

Ray of light is a Path along which light energy travels in a medium. It is represented by arrow on a straight line. Arrowhead represents the direction.

WHAT IS A BEAM OF LIGHT?

A group of rays is called a beam of light. Narrow beam is called a pencil (of light). Based on point of meeting & width of the pencil Beam can be of 3 kinds: a) Parallel Pencil. b) Convergent Pencil. c) Divergent Pencil. A highly polished surface which is smooth enough to reflect a good fraction of light incident on it is called a mirror. Common types of mirrors are Plane Mirror, Concave Mirror & Convex Mirror.

WHAT IS REFLECTION OF LIGHT?

When light travelling from one medium falls on the surface of another medium, a portion of incident light is turned back into the first medium. This is called reflection of light.

WHAT IS A SOURCE OF LIGHT?

A source of light is an object which emits light. Source of light can either be Natural or Artificial (manmade).

WHAT ARE THE NATURAL SOURCES OF LIGHT?

1. Nuclear Fusion - Sun & Stars 2. Bioluminescence – Light produced by chemical reactions within the organism – eg: Fireflies, jellyfish, glow-worm, 3. Lightening & Volcanic eruptions

WHAT ARE THE ARTIFICIAL SOURCES OF LIGHT?

There are 4 types of Artificial Sources of Light: Incandescent Sources of Light. Luminescent Sources of Light, Gas Discharge Sources of Light, LED Bulbs

ARTIFICIAL SOURCES OF LIGHT:

Incandescent Sources of Light:, when certain objects are heated to a high temperature, they begin to emit light. Both infrared and visible light is produced in the process. Eg: Incandescent lamp, Candle. 2. Luminescent Sources of Light: Light can be produced by passing electricity through a luminescent material. 3. Gas Discharge Sources of Light: Light can be produced by passing electricity through certain gases at very low pressure. Example – Vapor Lamps like Neon lamp, Sodium lamp.