A slit of width a is illuminated by white light. The first minimum for light of wavelength 3900 Å will fall at θ = 60°, if a is
Answer & explanation
Correct answer: option 4
For first minimum,
$a\sin θ = λ$
$⇒a=\frac{λ}{\sin θ}=\frac{3900}{\sin 60}Å=4503 Å$