What happens when waves pass through a gap equal to their wavelength?

Question 30

What happens when waves pass through a gap equal to their wavelength?

A There is diffraction and the wavelength decreases.

B There is diffraction and the wavelength stays the same.

C There is no diffraction and the wavelength decreases.

D There is no diffraction and the wavelength stays the same.

Reference: Past Exam Paper – November 2018 Paper 12 Q28

Solution:

Answer: B.

When the gap is equal in width to the wavelength of the wave, diffraction occurs. [C and D incorrect]

During diffraction, the wavelength stays the same as the wave has not changed medium. It has only passed through a gap. The distance between wavefronts remains constant. [B is correct]