Question

a plano convex lens has radius of 10cm and focal length 80cm under water .find the refractive index
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Answer 1

Answer:

Given information is,

R1 = 10 cm; R2 = ∞; f = 80 cm and μwater = 43

So, Focal length of the plano - convex lens, when it is immersed in water is,

1fw = (μrel−1)[1R1−1R2] ⇒ 180 = (μmμwater−1)[110−1∞] ⇒ 180 = (μm43/−1)[110] ⇒ 18 = (3μm4−1) ⇒ 3μm4 = 98⇒ μm = 32

Therefore, refractive index of the material is 1.5