11. Light Class 7 Science NCERT Notes for Chapter 11 CBSE

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Welcome to Light Class 7 Science NCERT Notes for Chapter 11 CBSE.

11 Light

Introduction

Light is a fascinating phenomenon that we encounter daily.
It can be observed in various forms, such as sunlight, beams from headlamps, torches, and more.
In this chapter, we will explore how light behaves and interacts with different surfaces and objects.

11.1 LIGHT TRAVELS ALONG A STRAIGHT LINE

Light travels in straight lines, as demonstrated by an experiment involving a candle, a straight pipe, and a bent pipe.
The experiment with Boojho showed that light doesn’t bend when it travels through a straight pipe but can’t pass through a bent pipe.

11.2 REFLECTION OF LIGHT

The direction of light can be changed by letting it fall on a shiny surface like a mirror.
Water surfaces also act as mirrors, reflecting objects, such as trees or buildings.
Mirrors change the direction of light, a phenomenon known as reflection of light.

Activity 11.1: Reflecting Light

Take a torch with a chart paper containing slits, a plane mirror, and a smooth wooden board.
Shine the torch’s light on the mirror, adjusting the angle to observe reflected light.
This activity demonstrates how light gets reflected from a plane mirror.

Activity 11.2: Image Formation

Place a lighted candle in front of a plane mirror.
Observe the image of the candle in the mirror, which appears as if there’s another candle behind it.
The image formed by a plane mirror is virtual, erect, and of the same size as the object.

11.3 RIGHT OR LEFT!

When you see your image in a plane mirror, left appears as right, and right appears as left.
This property is used, for example, in ambulance lettering, which is reversed so drivers can read it in their rearview mirrors.

11.4 PLAYING WITH SPHERICAL MIRRORS

Convex Mirrors

Convex mirrors form virtual, erect, and smaller images than the objects.
They are commonly used as side-view mirrors in vehicles to provide a wider field of view.

Concave Mirrors

Concave mirrors can form both real and virtual images.
The image size and nature vary with the object’s distance from the mirror.
They are used in various applications, including dental examinations and reflectors in torches.

11.5 IMAGES FORMED BY LENSES

Convex Lenses

Convex lenses can form real and inverted images.
They are used as magnifying glasses when an object is placed close to them.

Concave Lenses

Concave lenses always form virtual, erect, and smaller images than the objects.

11.6 SUNLIGHT — WHITE OR COLOURED?

Sunlight appears white but is actually composed of seven colors.
The colors can be separated using a prism, and this phenomenon is also observed in rainbows.
Mixing these colors can create white light again.

These notes cover the key concepts of the chapter “LIGHT” in a structured and informative manner, following the guidelines you provided.

Keywords and Definitions:

Convex Lens: A lens that bulges outward and converges light rays.
Concave Lens: A lens that curves inward and diverges light rays.
Virtual Image: An image formed by light rays that appear to converge from a point but do not actually meet.
Real Image: An image formed by light rays that actually converge and meet at a point.
Concave Mirror: A mirror with an inward-curving reflective surface that can form real or virtual images.
Convex Mirror: A mirror with an outward-curving reflective surface that forms virtual images.
Plane Mirror: A flat mirror that forms virtual, erect, and same-sized images.
Rainbow: A meteorological phenomenon that results in a spectrum of light appearing in the sky when sunlight is refracted, dispersed, and reflected by water droplets.
Newton’s Disc: A spinning disc with seven rainbow-colored segments that appear white when rotated rapidly.
Spherical Mirror: A mirror that is part of a sphere and includes both concave and convex mirrors.

Frequently Asked Questions (FAQs) with Answers:

What is a virtual image?

A virtual image is an image formed by light rays that appear to converge from a point but do not actually meet. Learn more

How does a convex lens differ from a concave lens?

A convex lens bulges outward and converges light rays, while a concave lens curves inward and diverges light rays. Learn more | Learn more

What kind of image does a concave mirror typically form?

A concave mirror can form real or virtual images, depending on the object’s position. Learn more

Describe the characteristics of an image formed by a plane mirror.

An image formed by a plane mirror is virtual, erect, and the same size as the object. Learn more

How is a rainbow formed in the sky?

A rainbow is formed when sunlight is refracted, dispersed, and reflected by water droplets in the atmosphere, creating a spectrum of colors. Learn more

What is Newton’s Disc, and how does it work?

Newton’s Disc is a spinning disc with seven rainbow-colored segments that appear white when rotated rapidly. It demonstrates the mixing of colors. Learn more

Can a convex mirror form a real image?

No, a convex mirror always forms a virtual image. Learn more

What is the difference between a real image and a virtual image?

A real image is formed by light rays that actually converge and meet at a point, while a virtual image appears to converge from a point but does not actually meet. Learn more

What are the common uses of concave and convex mirrors in everyday life?

Concave mirrors are used in applications like car headlights and makeup mirrors, while convex mirrors are used in rearview mirrors to provide a wider field of view. Learn more | Learn more

Explain the concept of a spherical mirror.

A spherical mirror is a mirror that is part of a sphere and includes both concave and convex mirrors, depending on the curvature of the mirror’s surface. Learn more

This was the end of Light Class 7 Science NCERT Notes for Chapter 11 CBSE.

For more information, refer to NCERT SOLUTIONS, NCERT NOTES, and NCERT BOOKS .