Question 121 markMCQSection A

At what distance from a convex lens should an object be placed to get an image of the same size as that of the object on a screen ?

Chemical Reactions and Equations
Light - Reflection and Refraction

Options

(a)Beyond twice the focal length of the lens.
(b)At the principal focus of the lens.
(c)At twice the focal length of the lens.
(d)Between the optical centre of the lens and its principal focus.

Official answer

The correct option is (c) At twice the focal length of the lens.

Answer keywords:Convex lensTwice the focal length2FSame size image

Marking scheme

  1. 1.1 mark for selecting the correct option (c).

Hint

Recall the ray diagram where the object and image are at symmetrical distances from the lens.

Quick oral answer

To get an image of the same size as the object using a convex lens, the object must be placed at a distance of 2f2f from the optical center.

Common mistakes

  1. 1.Confusing the focal length (ff) with twice the focal length (2f2f). Placing the object at ff results in an image at infinity, not same size.

Analysis and explanation

For a convex lens, the characteristics of the image depend on the object's position relative to the focal length (ff).

  • Option (c): When an object is placed at 2F2F (twice the focal length), the lens forms a real, inverted image on the other side at 2F2F. The size of this image is exactly the same as the size of the object.
  • Option (a): Beyond 2F2F, the image is diminished and formed between FF and 2F2F.
  • Option (b): At FF, the image is formed at infinity and is highly enlarged.
  • Option (d): Between OO and FF, the image is virtual, erect, and enlarged.

Interesting facts

This specific setup is often used in photocopiers to produce a 1:1 scale copy of a document.

Question details

Q12 of 39 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2024
Section
Section A
Marks
1
Type
MCQ
Chapter
Chemical Reactions and Equations
Topic
Light - Reflection and Refraction
Bloom's level
Remembering
Syllabus topic
Image Formation by Lenses

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Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 1 mark in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Light - Reflection and Refraction" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2024 paper.