Optics Question 194

Question: A slit of width a is illuminated by white light. For red light (λ=6500AA) , the first minima is obtained at θ=30o. Then the value of a will be

[MP PMT 1987; CPMT 2002]

Options:

A) 3250AA

B) 6.5×104mm

C) 1.24 microns

D) 2.6×104cm

Show Answer

Answer:

Correct Answer: C

Solution:

For first minima θ=λa or a=λθ

a=6500×108×6π (As 30o = π6 radian) =1.24×104cm=1.24 microns



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