71) An object placed at a distance of 30 cm in front of a concave mirror of focal length 20 cm. The image is formed at a distance of
72) Every lens has _________ focal points.
73) The radii curvatures of a double convex lens are 10 cm and 10 cm. Its refractive index is 1.5. The focal length is
View Answer
A) 10 cm
Explanation:R1 = 10, R2 = 10, n = μ = 1.5
∴ 1/f =
= 0.5 x[2/10] = 5/10×2/10 = 10/100 = 1/10 cm
F = 10 cm, f = 4, so image forms infinity
74) An object is placed 10 cm from a converging lens of focal length 10 cm. The image is formed at a distance of
75) A convex lens is placed in water. The focal length will
76) A light ray incident on curved surface travelling from rarer medium to denser medium bends _______ the normal.
77) Which part of human eye is called variable aperture?
78) In case of eye defect called ‘myopia’ image forms
79) In prism experiment, the i-d curve looks like
80) The splitting of white light into different colours is called
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