Question

an object is placed at a distance of 10cm from the pole of a concave mirror lmage is formed at 6cm from its pole .then the focal length of the mirror.

Answer 1

given,

u = -10 cm

v = -6 cm

use formula,

1/v + 1/u = 1/f

1/(-10) + 1/( -6) = 1/f

-16/60 = 1/f

f = - 60/16 = -15/4 cm

Answer 2

Given :

u = -10 cm
v = -6 cm
f = ?
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Using mirror formula ;

(1/f) = (1/v) + (1/u)
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1/f = (1/-6) + (1/-10)

1/f = (-5-3)/30

f = 30/-8

f = 15/-4

f = -3.75 cm
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The focal length of the concave mirror is 3.75 cm