The power of a lens is $-0.25 D$ . Based on this information, find out

(a) The type of lens and its focal length.

(b) The eye defect for which it may be used as a corrective lens.

(c) The nature and size of the image formed by this lens when an object is placed between F and 2F from the optical centre of this lens.

Q: The power of a lens is $-0.25 D$. Based on this information, find out (a) The type of lens and its focal length. (b) The eye defect for which it may be used as a corrective lens. (c) The nature and size of the image formed by this lens when an object is placed between F and 2F from the optical centre of this lens.

(a) The lens is concave and its focal length is $-4 m$. (b) The lens can be used to correct myopia (nearsightedness). (c) The image formed by this lens when an object is placed between F and 2F from the optical centre of this lens is real, inverted, and smaller than the object.

The Human Eye and the Colourful World

Refraction of Light

Official Answer

(a) The lens is concave and its focal length is $-4 m$ .

(b) The lens can be used to correct myopia (nearsightedness).

(c) The image formed by this lens when an object is placed between F and 2F from the optical centre of this lens is real, inverted, and smaller than the object.

concave lensmyopiareal imageinverted imagesmaller image

Hint

Recall the properties of concave lenses and the type of image they form when the object is placed between F and 2F from the optical centre.

Quick Oral Answer

The lens is concave and its focal length is $-4 m$ . The lens can be used to correct myopia. The image formed by this lens when an object is placed between F and 2F from the optical centre of this lens is real, inverted, and smaller than the object.

Analysis & Explanation

The power of a lens is related to its focal length. A concave lens has a negative focal length and is used to correct myopia. The image formed by a concave lens when an object is placed between F and 2F from the optical centre of this lens is real, inverted, and smaller than the object.

Common Mistakes

1Calculating the focal length incorrectly
2Incorrectly identifying the type of lens

Interesting Facts

Concave lenses are used in eyeglasses to correct myopia.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2025?

This question carries 3 marks in the CBSE Class 10 Science 2025 examination.

Which chapter does this question come from in Science?

This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Refraction of Light" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2025 paper?

This is a Short Answer question from Section C in the CBSE Class 10 Science 2025 paper.