Question

A convex lens of focal length 15 cm produces a magnification of +4. The
object is placed
a) at a distance of 15 cm
b) between 15 cm and 30 cm
C) at less than 15 cm
d) beyond 30 cm​

Answer 1

Answer:

A) between 15 cm and 30 cm is correct ANSWER

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Answer 2

Answer :

Focal length = 15cm

Magnification = +4

Type of lens : convex

We have to find distance of object$.$

★ Lateral Magnification :

⭆ m = v/u

• v denotes distance of image
• u denotes distance of object

⭆ 4 = v/u

⭆ v = 4u

★ Lens Formula :

⭆ 1/v - 1/u = 1/f

Focal length of convex lens is taken +ve and that for concave lens is taken -ve.

⭆ 1/4u - 1/u = 1/15

⭆ -3/4u = 1/15

⭆ u = -45/4

⭆ u = -11.25 cm

∴ (D) is the correct answer!

Cheers!