Question

Three thin convex lenses of focal length f1,f2,f3 are placed in contact coaxially. What will be
effective power of combination?​

Answer 1

Answer:

P = 1 / F(in meter)

= 1 / F( in cm )

Effective power = 1 / f1 + 1 / f2 + 1 / f3

[ LCM of f1 , f2 , f3 = f1 × f2 × f3]

hence, 1 / f1 + 1 / f2 + 1 / f3

= 1 (f2•f3) + 1(f1•f3) + 1(f1•f2)

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f1•f2•f3

THEREFORE,

EP = f1•f2 + f1•f3 + f1•f2

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f1•f2•f3

answer is in meter!!

Answer 2

Answer:

f1.f2+f1.f3+f1.f2/f1.f2.f3