In demonstrating diffraction with light through an aperture, why are there black spaces in between?

Question

In demonstrating diffraction with light through an aperture, why are there black spaces in between the light/line of light?

Answer 1

Assume a wave front arriving at the aperture. Constructive interference will create bright areas; destructive interference will give darkness. The interference arises from the different path lengths of the light (through different parts of the aperture) to the target. Some trigonometry using the wavelength of the light will permit calculation of the position of the bright bands.

Answer 2

Because light acts as a wave phenomena and the 'dark' areas are those in which the waves 'interfere' with each other. This is why it's also called an 'interferometeric' pattern

HTH ☺


Doug