Multiple shadow regions can be observed in the wall behind the keyhole of a door. Option B is correct.
It is a phenomenon that happens when a wave (Light) is passed through a narrow aperture or a sharp edge, the light bends at the edges.
The light bends at the edges because the sharp edges have less diameter than the wavelength of light.
Therefore, multiple shadow regions can be observed in the wall behind the keyhole of a door.
Learn more about diffraction:
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