An object is placed at a distance of 10 cm from a co-axial combination of two lenses A and B in contact. The combination forms a real image three times the size of the object. If lens B is concave with a focal length of 30 cm. The nature and focal length of lens A is

Options

(a) convex, 12 cm
(b) concave,12 cm
(c) convex, 6 cm
(d) convex, 18 cm

Correct Answer:

convex, 6 cm

Explanation:

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