An object is placed 10 m before a convex lens with a focal length 5.2 m. Another

Question

An object is placed 10 m before a convex lens with a focal length 5.2 m. Another convex lens is placed 20.5 m behind the first lens with a focal length 3.8 m.

(a) At what distance is the first image from the first lens? (Answer in units of m)

(b) What is the magnification of the first image?

(c) At what distance is the second image from the second lens? (Answer in units of m)

(d) What is the magnification of the final image, when compared to the initial object?

Explanation / Answer

1/f = 1/v + 1/u

1/v = 1/f - 1/u

1/v = 1/5.2 - 1/10

v = 10.83 m

part b )

m = -v/u

m = -10.83/10 = -1.083   

part c )

distance object = 20.5 - 10.82 = 9.68 m

1/v' = 1/f - 1/u'

1/v' = 1/3.8 - 1/9.68

v' = 6.26 m

part d )

m = -v'/u

m = -6.26/10 = -0.626

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