A 10 mm long pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is:

(a) - 30 cm

Given: ho =l0 mm , hi= 5mm = 0.5 cm and v = 30 cm To find : focal length of mirror Solution : We know that, Magnification = 1 - v/F Also, magnification = ho/hi Now, ho/hi = 1 - v/F, putting values we get 1/0.5 = 1 - 30/F 30/F= 1 - 10/5 = - 1 F = - 30cm Answer: Hence, correct option is (a) - 30 cm

Was this answer helpful?
0
0