CBSE Class 7 Science Chapter 15 Light NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 7 PDF

CBSE Class 7 Science Chapter 15: Light introduces students to the fascinating world of light and its properties. This chapter delves into how images are formed by various optical devices, including plane mirrors, convex mirrors, concave mirrors, convex lenses, and concave lenses. You'll learn about the characteristics of these images, such as whether they are real or virtual, erect or inverted, and magnified or diminished. The solutions explore the concept of lateral inversion, explaining why a plane mirror seems to swap left and right. Understanding these principles is crucial for grasping how we see the world around us and how optical instruments like telescopes and microscopes work. These NCERT Solutions provide clear, step-by-step explanations to help you master the concepts and answer all exercise questions with confidence, preparing you thoroughly for your exams.

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Quick info

Board	CBSE
Class	Class 7
Subject	Science
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 15: Light

Chapter summary

Chapter 15 of the NCERT Class 7 Science textbook focuses on Light. This chapter's solutions cover the properties of light, the formation of images by various optical devices like plane mirrors, convex mirrors, concave mirrors, convex lenses, and concave lenses. It explains the difference between real and virtual images and details the characteristics of images formed by each type of mirror and lens, including magnification, inversion, and lateral symmetry. The exercises also touch upon practical applications and observations related to light.

Learning outcomes

Understand the difference between real and virtual images.
Identify the types of images formed by plane mirrors, convex mirrors, concave mirrors, convex lenses, and concave lenses.
Describe the characteristics of images formed by different optical devices.
Explain the concept of lateral inversion.
Recognize letters of the alphabet that are laterally symmetrical.

Topics covered

Paper topics

Light
Image formation
Real image
Virtual image
Plane mirror
Convex mirror
Concave mirror
Convex lens
Concave lens
Image characteristics
Lateral inversion
Symmetry of letters

Important topics

Real vs. Virtual Images
Image Formation by Plane Mirrors
Image Formation by Concave Mirrors
Image Formation by Convex Mirrors
Image Formation by Lenses
Lateral Inversion

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Questions and Solutions

Question 1

Fill in the blanks: (a) An image that cannot be obtained on a screen is called _____. (b) Image formed by a convex _____ is always virtual and smaller in size. (c) An image formed by a _____ mirror is always of the same size as that of the object. (d) An image which can be obtained on a screen is called a _____ image. (e) An image formed by a concave _____ cannot be obtained on a screen.

Solution: (a) An image that cannot be obtained on a screen is called a virtual image. Virtual images are formed where light rays only appear to meet and cannot be projected onto a screen. (b) Image formed by a convex mirror is always virtual and smaller in size. Convex mirrors are used as rear-view mirrors because they provide a wider field of view. (c) An image formed by a plane mirror is always of the same size as that of the object. Plane mirrors also produce erect and laterally inverted images. (d) An image which can be obtained on a screen is called a real image. Real images are formed by the actual convergence of light rays and can be projected onto a surface. (e) An image formed by a concave lens cannot be obtained on a screen. A concave lens always forms a virtual, erect, and diminished image.

Question 2

Mark 'T' if the statement is true and 'F' if it is false: (a) We can obtain an enlarged and erect image by a convex mirror. (T/F) (b) A concave lens always form a virtual image. (T/F) (c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F) (d) A real image cannot be obtained on a screen. (T/F) (e) A concave mirror always form a real image. (T/F)

Solution: (a) False (F). A convex mirror always forms a virtual, erect, and diminished image. (b) True (T). A concave lens always forms a virtual, erect, and diminished image. (c) True (T). A concave mirror can form a real, enlarged, and inverted image when the object is placed between its pole and focal point. (d) False (F). A real image can be obtained on a screen because it is formed by the actual intersection of light rays. (e) False (F). A concave mirror can form both real (when the object is placed beyond the focal point) and virtual images (when the object is placed between the pole and focal point).

Question 3

Match the items given in Column I with one or more items of Column II. Column I (a) A plane mirror (b) A convex mirror (c) A convex lens (d) A concave mirror (e) A concave lens Column II (i) Used as a magnifying glass. (ii) Can form image of objects spread over a large area. (iii) Used by dentists to see enlarged image of teeth. (iv) The image is always inverted and magnified. (v) The image is erect and of the same size as the object. (vi) The image is erect and smaller in size than the object.

Solution: The correct matches are:

(a) A plane mirror matches with (v) The image is erect and of the same size as the object. A plane mirror forms an erect image of the same size as the object.
(b) A convex mirror matches with (ii) Can form image of objects spread over a large area. Convex mirrors provide a wide field of view, allowing them to show a larger area. They form virtual, erect, and diminished images.
(c) A convex lens matches with (i) Used as a magnifying glass. A convex lens can form a magnified, erect, and virtual image when the object is placed within its focal length. It can also form real images.
(d) A concave mirror matches with (iii) Used by dentists to see enlarged image of teeth. A concave mirror forms an enlarged, erect, and virtual image when the object is placed between its pole and focal point.
(e) A concave lens matches with (vi) The image is erect and smaller in size than the object. A concave lens always forms a virtual, erect, and diminished image.

Note: Option (iv) 'The image is always inverted and magnified' is not a direct match for any single item but can describe some images formed by a concave mirror or convex lens under specific conditions, though not exclusively.

Question 4

State the characteristics of the image formed by a plane mirror.

Solution: The characteristics of the image formed by a plane mirror are:

Virtual: The image cannot be projected onto a screen.
Erect: The image is upright, meaning it has the same orientation as the object.
Same Size: The image is of the same dimensions as the object.
Laterally Inverted: The image is reversed from left to right. For example, the left side of the object appears as the right side of the image.
Image Distance: The image is formed behind the mirror at the same distance as the object is in front of the mirror.

Question 5

Find out the letters of the English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.

Solution: The letters of the English alphabet that appear exactly like themselves when their image is formed in a plane mirror are those that are laterally symmetrical. These letters have a vertical line of symmetry, meaning the left half is a mirror image of the right half. The letters are: A, H, I, M, O, T, U, V, W, X. For example, the letter 'A' looks the same whether viewed directly or as its reflection in a plane mirror. This is because the reflection does not change its appearance due to its symmetrical nature.

Question 6

What is a virtual image? Give one situation where a virtual image is formed.

Solution: A virtual image is an image that is formed when the rays of light appear to diverge from a point but do not actually meet or converge there. Because the light rays do not actually intersect, a virtual image cannot be projected onto a screen. One common situation where a virtual image is formed is when an object is placed in front of a plane mirror. The image seen in a plane mirror is always virtual, erect, and laterally inverted. Other examples include the image formed by a convex mirror and the image formed by a concave lens.

Common mistakes

Confusing real and virtual images.
Incorrectly identifying the type of image formed by a specific mirror or lens.
Misunderstanding the properties of images (size, orientation, position).
Difficulty in applying the concept of lateral inversion.

Revision tips

Draw ray diagrams to visualize image formation by different mirrors and lenses.
Create a table summarizing the characteristics of images formed by each optical device.
Practice identifying whether an image is real or virtual based on its properties.
Focus on understanding lateral inversion with examples like letters of the alphabet.

Practice MCQs

Q1. Which type of image cannot be obtained on a screen?

Q2. A convex mirror always forms an image that is:

Q3. Which optical device is used by dentists to see an enlarged image of teeth?

Q4. The image formed by a plane mirror is:

Q5. Which of the following English alphabet letters are laterally symmetrical?

Frequently asked questions

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

A real image can be formed on a screen because the light rays actually converge at the image point. A virtual image cannot be formed on a screen as the light rays only appear to diverge from the image point.

What kind of image does a plane mirror form?

A plane mirror forms an image that is virtual, erect, the same size as the object, and laterally inverted. The image is formed behind the mirror at the same distance as the object is in front.

Which mirror is used by dentists?

Dentists use a concave mirror. This is because a concave mirror can form an enlarged, erect, and virtual image of an object when it is placed within its focal length, allowing dentists to see details clearly.

Can a convex lens always form a real image?

No, a convex lens can form both real and virtual images. It forms a real, inverted image when the object is placed beyond the focal point, and a virtual, erect, and magnified image when the object is placed between the optical center and the focal point.

What does 'laterally inverted' mean for an image in a plane mirror?

Lateral inversion means that the image formed by a plane mirror is reversed from left to right. For example, if you raise your right hand, the image appears to raise its left hand.

Which letters of the English alphabet are symmetrical in a plane mirror?

Letters like A, H, I, M, O, T, U, V, W, and X appear exactly the same as their image in a plane mirror because they possess vertical symmetry.

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