Question

an object 3cm high is placed at a distance of 20 cm in front of a convex lens of focal length 12 cm. Find the position , nature and size of image so formed​

Answer 1

Answer:Now as we know that the formulae of convex lens =1/v-1/u=1/f

As, we have, v=?, u= -20cm, f=12cm, h= 3cm

Now use these all values in the formulae as shown above,

, 1/v-1/-20=1/12

1/v+1/20=1/12 (1/v-1/-20=1/+20)

Now, 1/v=1/12-1/20

1/v=5-3/60

1/v=2/60

V=60/2 (by doing reciprocal in both sides)

V=30cm

Now we also given h

Such that m=h'/h=v/u

,h'/3=30/-20

, h'=30×3/-20

, h'=90/-20

, h'= -4.5cm

Explanation: