If the power of a lens is + 0.1 D and if an object of size 2 cm is placed 5 cm before the lens. Find the size and position of the image formed?
Image size = 4 cm, image distance = – 10 cm
Given, power, P=0.1 D
Object distance, u=−5 cm
Let v be the image distance and f be the focal length.
P = 1f ⇒ f = 10 cm
Using lens formula,
1v - 1u = 1f
1v - 1(−5) = 1(10) ⇒ 1v = 110 = −110
v = - 10 cm
Height of object, h=2 cm
Let h′ be height of object.
We know,
vu = h′h ⇒ −10(−5) = h′2
h′ = 4 cm
Image height = 4 cm