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SAI INTERNATIONAL SCHOOL
Class 7
Lesson Notes
Subject-Physics
CH: Light and Associated Phenomena
Subtopic- Rectilinear Propagation & Types of Reflection

LIGHT
Light is a form of energy which enables us to see objects.
Source of Light:
The object which gives out or emits light is called source of light.
Natural: Sun, Stars, Firefly.
Artificial: Torch, Tube light, LED

Rectilinear Propagation of Light:
The property which states that light always travels in a straight line is called
rectilinear propagation of light.
 Shadow formation is due to or is a consequence of rectilinear propagation
of light.
 Some example of rectilinear propagation of light are: Light from torch,
headlights of car, Sun rays etc.
Reflection of light
Bouncing back of light after striking a surface is called reflection of light.
Types of reflection
Based on the surface from where light is reflected, reflection can be
classified into two types.
1. Regular reflection
2. Irregular/Diffused reflection
1. Regular reflection
Regular reflection takes place from polished surface.
In this type of reflection
 Parallel incident rays give parallel reflected rays.
 It leads to image formation.
Ex: plane mirror, highly polished metal surface, still water

2. Irregular/Diffused reflection