Question

Q33. An object of height 5 cm is held 30 cm away from a converging lens of focal length
10 cm. Find the position, size and nature of the image formed.
​

Answer 1

Explanation:

Given, u=-20cm

f=10cm

v=?

We know

f

1

=

v

1

−

u

1

10

1

=

v

1

−

20

(−1)

v

1

=

20

2−1

v=20cm

We know

magnification (M)=

h

o

h

i

=

u

−v

or,

−20

20

=−1=

h

o

h

i

since,h

0

=5cm

so,h

i

=−5cm

nature = real image

Answer 2

Answer:

To find position and height of image .

1/f = 1/v - 1/u

1/10 = 1/v - 1/(-30)

1/10 = 1/v + 1/30

1/v = 1/10 - 1/30

1/v = 3-1/30

1/v = 2/30

1/v = 1/15 [ cross multiplication ]

v = 15

ho/hi = v/u

ho/5 = 15/-30

ho = 15×5/30

ho = 2.5cm