Question

An object at a distance of 30cm
from acon cave mirror gets its image at
some point, the focal length
of the mirror is
[1].-30cm

[2].30 cm. [3]- 15 cm
[4].+ 15 cm​

Answer 1

Correct Question !!

An object is placed in front of concave mirror at a distance of 30cm from a concave mirror gets its image at same point, the focal length of the mirror is

Given:-

• Object distance ,u = +30 cm

• Image distance ,v = 30 cm

To Find:-

• Focal Length ,f

Solution:-

we have to calculate the focal length of the mirror

Using mirror formula

❒• 1/v + 1/u = 1/f

where,

v is the Image Position

u is the object distance

f is the focal length

Substitute the value we get

→ 1/30 +1/30 = 1/f

→ 1/f = 1/30 +1/30

→ 1/f = 1+1/30

→ 1/f = 2/30

→ 1/f = 1/15

→ f = 15cm

Therefore,the focal length of the mirror is 15 cm.

hence, the required answer is (4) 15 cm.