Question

An object is placed at a certain distance on the principal axis of concave mirror. The image is formed at
a distance of 30 cm from the minor. Find the object distance if r = 15 cm​

Answer 1

Here is your answer

Distance cannot be negative, so distance of object is 10cm

Answer 2

Explanation:

Given: Image distance, v = - 30 cm [ Concave.

Radius of Curvature, r = 15 cm

Object distance, u= ?

Since, Radius, r = 15 cm

Therefore, Focal length, f = -15/2 cm

-----[Concave mirror]

Now,

Using mirror formula,

=> 1 / f = 1/v +1/u

=> 1 / -15/2 = 1/ -30 + 1/u

=> 2 / -15 = 1/-30 + 1/u

=> -2 / 15 = -1/30 + 1/u

=> -2 / 15 + 1/ 30 = 1/u

=> 1/u = -4 + 1/ 30

=> 1/u = -3/30

=> 1/u = -1/10

=> [ u = -10 cm ]

Hence, Object distance, u = -10 cm

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