Question

Question:a Plano convex lens of radius 3 cm is placed on an optically flat glass plate an illuminated by monochromatic light the diameter of the 8 bright ring in the transmitted system is 0.72 to CM .calculate the wavelength of light used

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Answer 1

The radius of bright ring is given by formula

$r_k=\sqrt {\frac{(2k-1)Rλ}{2}} (1)$

In our case, k=8, R=3 cm, r₈=0.36 cm

Using (1) we get

λ=0.192 m

Answer

0.192 m