Question

a concave mirror has a focal length of 20cm.At what distance from the mirror should a 4cm tall object be placed so that it forms an image at adistance of 30cm from the mirror?also calculate the size of the image formed.​

Answer 1

Answer:

the object distance is 60cm and image height is 2cm

Explanation:

the focal length of concave mirror is 20cm

the image distance is 30cm

so, we know 1/u +1/v=1/f

so putting values we get

1/u=1/20 -1/30

or, 1/u =1/60

or, u=60

the object distance is 60cm

again, we know the object height=4cm

object distance =60cm and image distance=30cm

we know, image distance /object distance =image height /object height

By putting values and taking image height =I we get

30/60=I/4

or, I=2

the image height 2cm