Question

An object 3.0 cm high placed perpendicular to the principal axis of a concave lens if focal length 15.0 cm image is formed at a distance of 10.0cm from lens calculate the distance at which the object is placed and size and nature of image formed.

Answer 1

Answer:

u=−12cm

f=+8cm

ho=+3cm

Using mirror formula,

v

1

+

u

1

=

f

1

v

1

+

−30

1

=

8

1

v

1

−

30

1

=

8

1

v

1

=

8

1

+

30

1

v

1

=

60

3+2

v

1

=

60

5

=

12

1

v=+12cm

Therefore, the image will be formed at a distance of 12cm behind the mirror.

m=

um

−v

=

−30m

−12

=+0.4

m=

h

o

h

i

0.4=

h

o

h

i

0.4=

1

h

i

h

i

=+0.4cm

Therefore, the image formed is diminished in size.