Class 7 Science

Chapter 15: Light

STAGE 0: Foundation / Basics

Light is a form of energy that helps us to see objects.

Objects are visible to us because of light.

Sources of Light

Objects that give out light are called luminous objects.

• Sun
• Electric bulb
• Candle

Objects that do not give light are called non-luminous objects.

Reflection of Light

The bouncing back of light from a surface is called reflection.

A smooth and shiny surface reflects light well.

Plane Mirror

A plane mirror forms an image that is:

• Erect (upright)
• Same size as object
• Laterally inverted

Lateral Inversion

In a mirror, the left side of an object appears as right and vice versa.

This effect is called lateral inversion.

Shadow

A shadow is formed when an opaque object blocks the path of light.

Conditions for shadow:

• Source of light
• Opaque object
• Screen

Rainbow

A rainbow is formed due to the dispersion of sunlight by water droplets.

Colours of rainbow (VIBGYOR):

• Violet
• Indigo
• Blue
• Green
• Yellow
• Orange
• Red

STAGE 2: NCERT Textbook Questions & Answers

Q1. What is light?

Light is a form of energy that helps us to see objects.

Q2. What is reflection?

Reflection is the bouncing back of light from a surface.

Q3. What is lateral inversion?

Left appears right and right appears left in a mirror.

STAGE 3: Exam-Oriented Questions

Fill in the blanks:

• Objects that give light are called __________ objects.
• Bouncing back of light is called __________.

Very Short Answer:

Name one luminous object.
Answer: Sun

Quick Revision Points

• Light helps us see
• Reflection is bouncing of light
• Plane mirror shows lateral inversion
• Rainbow has seven colours