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Solved 2025 Specimen Paper ICSE Class 10 Physics — Question 19

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Question

Question 3(i)

(a) Refer to the diagram given below. A lens with two different refractive indices is shown. If the rays are coming from a distant object, then how many images will be seen?

The adjacent diagram shows the movable block of a block and tackle system with effort in a convenient direction. From the diagram we can conclude that the number of pulleys used in the fixed block are.ICSE 2025 Specimen Physics Solved Question Paper.

(b) A glass lens always forms a virtual, erect and diminished image of an object kept in front of it. Identify the lens.

Answer

(a) According to the lens maker formula :

1f=(μ−1)(1R1−R2)\dfrac{1}{\text f} = (\text μ - 1)\left(\dfrac{1}{\text R_1-\text R_2}\right)

Focal length is a function of refractive index, hence for two different refractive indices there will be two different focal lengths.

Two different focal length implies two different images for same object.

Hence, 2 images will be formed.

(b) Concave lens because irrespective of the position of the object, the image formed by a thin concave (or divergent) lens is always virtual, upright, diminished, and it is situated on the side of the object between the focus and the lens.

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