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The focal length of field achromatic com...

The focal length of field achromatic combination of a telescope is `90 cm` .The dispersive powers of lenses are `0.024` and `0.036` respectively .Their focal lengths will be-

A

30 cm and 60 cm

B

30 cm and -45 cm

C

45 cm and 90 cm

D

15 cm and 45 cm

Text Solution

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The correct Answer is:
b
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