Question

Two planoconvex lenses of glass of refractive index 1.5 have radii of curvature 20 cm and
30 cm. They are placed in contact with curved surfaces towards each other and the space
between them is filled with a liquid of refractive index 4/3. The focal length
combination is
a) 48 cm
b) 72 cm
c) 12 cm
d) 28 cm​

Answer 1

Answer:

a 48 ok.

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