Question

a 3.5cm high object is placed at a distance of 12cm from a concave lens of focal length 16cm find the position and size of the image

Answer 1

1/f=1/v-1/u
1/-16=1/v-1/-12
position of image=-48/7

size of image= -48*3.5/7*-16
size of image= 1.5cm

Answer 2

Explanation:

It is given that,

Focal length of the convex mirror, f = -16 cm

Distance of the car from the lens, u = -12 cm

Let v is the image distance. It can be calculated as :

$\dfrac{1}{v}=\dfrac{1}{f}-\dfrac{1}{u}$

$\dfrac{1}{v}=\dfrac{1}{-16}-\dfrac{1}{(-12)}$

v = 48 cm

So, the image is location at a distance of 48 cm from the mirror.

Magnification of the mirror,

$m=\dfrac{-v}{u}=\dfrac{h'}{h}$

h' is the size of the image

$\dfrac{-48}{-12}=\dfrac{h'}{3.5}$

h' = 14 cm

Hence, this is the required solution.