Question

A 5.75 mm high firefly sits on the axis of, and 11.3 cm in front of, the thin lens A, whose focal length is 5.77 cm . Behind lens A there is another thin lens, lens B, with a focal length of 27.9 cm . The two lenses share a common axis and are 59.9 cm apart.?

Answer 1

given,

focal length of lens A = 5.77 cm

focal length of lens B= 27.9 cm

flies distance from mirror = 11.3 m

now,

Using lens formula

`(1)/(f) = (1)/(p) + (1)/(q)`

`(1)/(5.77) = (1)/(11.3) + (1)/(q)`

q =11.79 cm

image of lens A is object of lens B

distance of lens = 59.9 - 11.79 = 48.11

now, Again applying lens formula

`(1)/(f) = (1)/(p) + (1)/(q')`

`(1)/(27.9) = (1)/(48.11) + (1)/(q')`

q' =66.41 cm

hence, the image distance from the second lens is equal to q' =66.41 cm