Question

Parallel wave fronts are incident on an opening in a barrier. Which diagram shows the configuration of wave fronts and barrier opening that will result in the greatest diffraction of the waves passing through the opening? [Assume all diagrams are drawn to the same scale.]

Answer 1

By looking at the diagram you posted above and reading the given information. Diagram number 2 shows the configuration of wave fronts and barrier opening. This graph number 2 shows the greatest diffraction of the waves through the opening. <span />

Answer 2

Explanation :

It is given that, parallel wave fronts are incident on an opening in a barrier. Diffraction of the waves depends on the size of opening and the wavelength of light used as per the following relation :

$y\propto\dfrac{\lambda}{a}$

where,

$\lambda$ is the wavelength of light

and a is the opening size (from fig)

So, it is clear that diffraction of waves depends directly on the wavelength of light and inversely on the size of opening.

Hence, the correct option is (2).