Question

two lens are in the ratio 4:1 what would be the focal length .​

Answer 1

Answer:

For an achromatic combination,

w

1

f

1

+

w

2

f

2

=0

Also, the effective focal length of the combination will be:

f

1

=

f

1

1

+

f

2

1

Solving these simultaneously and substituting the values, the obtained focal lengths are, f

o

=15 and f

e

=−20