Question

When an object is placed in front of a concave mirror at a

distance 30 cm ,an image is obtained on a screen at a distance

of 20 cm from the mirror. what is the focal length of the mirror?​

Answer 1

Answer:

Here given that,

u= -30 cm

f= -20 cm

By using mirror formula,

1/v + 1/u = 1/f

1/v + 1/-30 = 1/-20

v= -60 cm

negative sign indicates that image is in front of the mirror

Therefore,

The distance between image and object = 60–30 = 30cm

Hope this answer is helpful for you.

Answer 2

Answer:

v=20,u is not given and f=30

the focal length is -12