Question

A small aperture is illuminated with a parallel beam of $\lambda$ = 628nm . The emergent beam has an angular divergence of 2$^\circ$ . The size of the aperture is.

• A. $9\,\mu m$
• B. $18\,\mu m$
• C. $27\,\mu m$
• D. $36\,\mu m$

Answer 1

Answer: (D)

$36\,\mu m$

Answer 2

$a$ sin $\theta = n\lambda$ ; $\theta = \frac{\lambda}{a} \frac{n \pi }{180} rad$