An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is 25 D. Focal length of each of the convex lens is [2024]
20 cm
50 cm
25 cm
500 cm
(A) We know that
As given all lenses are identical, 5P = 25 D
Given below are two statements:
Statement (I): When an object is placed at the centre of curvature of a concave lens, image is formed at the centre of curvature of the lens on the other side.
Statement (II): Concave lens always forms a virtual and erect image.
In the light of the above statements, choose the correct answer from the options given below: [2024]
Statement I is false but Statement II is true.
Both Statement I and Statement II are false.
Statement I is true but Statement II is false.
Both Statement I and Statement II are true.
(A) Statement-I is False. (Image is formed on the same side, not on the other side).
Statement-II is True. (As object is real, its virtual and erect image is formed).
A biconvex lens of refractive index 1.5 has a focal length of 20 cm in air. Its focal length when immersed in a liquid of refractive index 1.6 will be: [2024]
-16 cm
-160 cm
+160 cm
+16 cm
(B)
