Question

An object is placed vertically on the principal axis at a distance of 20 cm in front of a concave lens of focal length 30cm find the position of the image.​

Answer 1

Answer:

1.2cm

Explanation:

we know

1/ f= 1/v+ 1/ u

where v is image distance

u is object distance

f is focal length

now

1/30=1/v+1/(-20)

1/30= 1/v- 1/20

1/30+1/20= 1/v

20+30/60= 1/v

50/60=1/v

5/6= 1/v

6/5= v

therefore

v= 1.2cm

Answer 2

Answer = -12cm

Explanation: f= -30

U= -20

V= ?

We know,1/f= 1/v - 1/u

1/v = 1/-3o+1/-20

1/v = -20 /600+ (-30)/600

1/v = -50/600

1/v = -1/12

V= -12