Question

A concave mirror of focal length 20cm form an image having twice the size of object will be at:(a.) 15(b.) 20(c.) 30(d.) 0​

Answer 1

The correct option is (C) 10.

Explanation:

Focal length of concave mirror = f = 20 cm

magnification = m = 2

m = (–v / u)

∴ 2 = (–v / u)

Hence v = –2u .....(1)

Also (1/f) = (1/v) + (1/u)

∴ (1/f) = (1 / –2u) + (1/u)

(1/f) = {(– 1 + 2) / (2u)} = (1 / 2u)

∴ 20 = 2u

u = 10 cm i.e. position of object is 10 cm.

See the image

Answer 2

ok bhai

toh aao bhi apne irrelevant ques bhi qpni pas rakho post mat karo

varna kuch ho jye gya

mujhe nahi aap ko

$\huge\mid\mathcal\green{Khushi}$

Jai Masih Ki