Question

The correct relation between the size of the obstacle and wavelength of light in order to observe the diffraction effect is

• A. $a_{{}^{/}\lambda }=0$
• B. $a_{{}^{/}\lambda }=0^{.}$
• C. $a_{{}^{/}\lambda }=\infty$
• D. $a_{{}^{/}\lambda }=150$

Answer 1

Answer: (D)

$a_{{}^{/}\lambda }=150$

The wavelength of light used must be very small compared to the slit size.

If the slit size (or distance between two slits) is much smaller than the wavelength, it effectively acts like a single point and the waves propagate radially in all directions. If the slit size is much larger than the wavelength, it's like "no slit" – free propagation – and rays may propagate through the slit (almost) without disturbance.