Question

The focal length of an achromatic combination of two lenses is contact in 150 cm if the dispersive power of materials of the two lenses are 0.018 and 0.0 27 calculate the focal lengths of the two lenses?

Answer 1

Answer:

Correct option is

B

30 cm and −45 cm

For achromatic combination

f

2

f

1

=−

ω

1

ω

2

=−

0.024

0.036

=−

2

3

and

f

1

1

−

f

2

1

=

90

1

solving above equation be get f

1

=30 cm, f

2

=−45 cm

Answer 2

Answer:

correct option is b

Explanation:

b

is

the

correct

ans