Question

An object of 0.5centimeters in size is placed at a distance of 20 centimeters away from the concave mirror of focal length 15.0centimeters. At what distance from the mirror should a screen be placed to get sharp image. Also find the size of the image.

Answer 1

Answer: Now in this question we have to find the image distance which is v.

Now formulae if mirror =1/v+1/u=1/f.(1)

Now f= -15cm, u=-20cm, v=?,

Now put these all values in 1 equation,

1/v+1/-20=1/-15

Now, 1/v=1/-15+1/20,

, 1/v=-4+3/60

Then, 1/v=-1/60cm

Then by doing reciprocal we get,

V= -60cm.

Then size of image =

m=h'/h=v/u

m=0.5/h=-60/-(-20)

Then, h= 0.5×20/-60

h= -0. 16cm

Now we all values to find m,

So m=0.16/0.5

So, m= 0.32cm .

Explanation: