Question

an object 2 cm tall stands on principal axis of converging lens of focal length 8cm . find position, nature ,size of image formed if object is
1. 12 cm from lens
2. 6cm from lens

Answer 1

h =2cm
f= +8cm
convex lens
of u= -12 cm
1/v-1/u = 1/f
1/v - 1/-12 = 1/ 8
1/v = 1/8 - 1/12
1/v = 3-2/24
1/v = 1/24
v= 24
m= v/u = h'/h
24/-12=h'/2
24x2/-12 = h'
-4 = h'
the image is real inverted

Answer 2

Answer:converging lens is a convex lens

Given:

Focal length (f) = + 8cm

Height of the object (h) = +2 cm

(A)

(i) object distance (u) = - 2 cm

Lens formula is given as

1÷f = 1÷v - 1÷u

1÷8=1÷v-1÷-12

1÷u=1÷8-1÷12

1÷v=3-2÷24

1÷v=1÷24

V=24 cm

Image is at a distance of 24cm from the convex lens, therefore, we have

M=v÷u

M= 24÷-12

M=-2

Hence, the image is real and inverted

(B) object distance (u) = -6

According to lens formula :

1÷f= 1÷v -1÷u

1÷8=1÷v-1÷-6

1÷8=1÷v+1÷6

1÷8-1÷6=1÷v

3-4÷24=1÷v

-1÷24=1÷v

V=-24cm

Image is at a distance of 24cm in front of the lens: therefore, we have

M=v÷u

M=-24÷6

M=4

M=hi÷ho

M=hi÷2

Hi=2×4

Hi=8cm

Explanation:height of the image is 8cm

Here, height is positive ,therefore, image is virtual and erect