Chapter 15 – Light

These NCERT Class 7 Science Chapter 15 notes explain the importance of light and how it helps us see objects around us. The chapter introduces light as a form of energy and explains how objects become visible due to reflection of light.

Light also explains reflection, plane mirrors, image formation, and lateral inversion with simple daily-life examples. The chapter further introduces sunlight, dispersion of light, and formation of rainbow in a clear and student-friendly manner.

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1. Introduction: why light is important

•  Light helps us see objects around us.
•  Without light, our eyes cannot function.
•  This chapter explains the nature of light and image formation.
•  Light is the reason the world is visible.

2. What is light

•  Light is a form of energy.
•  Light travels in a straight line.
•  Objects are visible when light reflects from them and enters our eyes.

3. Luminous and non-luminous objects

•  Luminous objects produce their own light, like the Sun and electric bulb.
•  Non-luminous objects do not produce light, like the Moon, book, and table.
•  Non-luminous objects are seen because they reflect light.

4. Reflection of light

•  Reflection is the bouncing back of light from a surface.
•  Smooth surfaces reflect light better.
•  Mirror and calm water show good reflection.

5. Mirror

•  A mirror is a smooth and shiny surface.
•  It reflects most of the light falling on it.

6. Image formation by a plane mirror

•  The image formed is virtual and cannot be caught on a screen.
•  The image is erect and of the same size as the object.
•  The image appears at the same distance behind the mirror.
•  The image shows lateral inversion.

7. Lateral inversion

•  In lateral inversion, the left side appears right and the right side appears left.
•  Ambulance is written in reverse to be read correctly in mirrors.

8. Multiple images

•  Multiple images are formed when two or more mirrors are placed at angles.
•  Barber shops use this effect to show many images.

9. Sunlight and composition of light

•  Sunlight is made of seven colours.
•  These colours together form white light.
•  The colours are VIBGYOR – violet, indigo, blue, green, yellow, orange, and red.

10. Dispersion of light

•  Dispersion is the splitting of white light into seven colours.
•  Rainbow and glass prism show dispersion.

11. Rainbow formation

•  A rainbow is formed due to dispersion and reflection of sunlight.
•  It is seen after rain when the Sun shines.

12. Spherical mirrors

•  Concave mirrors bend light inward.
•  Convex mirrors spread light outward.
•  Detailed ray diagrams are not required at this level.

13. Uses of mirrors

•  Plane mirrors are used as dressing mirrors and looking glasses.
•  Concave mirrors are used in torches and vehicle headlights.
•  Convex mirrors are used as rear-view mirrors in vehicles.

14. Importance of reflection

•  Reflection helps us see objects.
•  It is used in optical instruments.
•  It helps in safety and transport.

15. Important keywords with simple definitions

•  Light – form of energy that helps us see.
•  Reflection – bouncing back of light from a surface.
•  Plane mirror – flat mirror that forms virtual images.
•  Image – picture formed by reflection of light.
•  Lateral inversion – left-right reversal in mirror image.
•  Dispersion – splitting of white light into colours.
•  Spectrum – band of seven colours of white light.

Understanding NCERT Class 7 Science Chapter 15 – Light is important to learn how images are formed and how light behaves when it strikes different surfaces. The chapter clearly explains reflection, mirrors, and dispersion of light.

These concepts are frequently asked in school examinations and are useful for foundation-level science preparation. Students should next read Chapter 16: Water – A Precious Resource to understand importance, availability, and conservation of water.

FAQs

Q1. What is explained in NCERT Class 7 Science Chapter 15?
The chapter explains light, reflection, image formation, and dispersion of light.

Q2. What is reflection of light?
Reflection is the bouncing back of light after it strikes a surface.

Q3. What is lateral inversion?
Lateral inversion is the left-right reversal seen in images formed by a plane mirror.

Q4. What is dispersion of light?
Dispersion is the splitting of white light into seven colours.

Q5. Why is NCERT Class 7 Science Chapter 15 important for exams?
It explains basic concepts of light and mirrors that are commonly asked in school and foundation-level exams.

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