a concave lens has focal length of 20cm.at what distance from the lens a 5 cm tall object be placed so that it form an 15cm from the lens ? also calculate the size of the image formed.
Answers
Answered by
4
Answer:
Focal length of the lens=f=20cm
Object - distancee= u=?
Image distance=v=15cm
object height = h_{o} =5cm
Image height= h_{i} =?
1/f=1/v-1/u
1/u=1/v-1/f
1/u=1/15-1/20
1/u=4-3/60
1/u=1/60
u=60cm
Therefore the object must be placed at a distance of 60cm from the lens
v/u= h_{i}/ h_{o}
h_{i} =15/60*5=5/4=1.25cm
Similar questions