Start by playing with the light interference simulation for a few minutes. Click on the “Slits” tab and select the laser. On the right hand side, increase the number of slits to two.
If you have not done so already, check the “screen” button and the “intensity” button. How does what you see on the screen compare to the lines of maximum constructive or destructive interference you identified?
Try at least 5 different colors of light. If you measure the distance between the sources as a number of wavelengths, does this number of wavelengths increase, decrease, or remain the same when you increase the frequency. Explain your reasoning.
Devise a qualitative rule for how the distance between bright spots on the screen depends on the wavelength of the light. (Recall that frequency and wavelength are related by the wave speed.)
A powerful wave property allows complicated light waves to be treated as superpositions of simpler light waves. In particular, any wave front of light can be treated as a collection of point sources of spherical waves, an idea known as Huygen’s Principle.
Figure19.2.2.A diagram of Huygen’s Princple. As light travels through an opening, each point along a wave front can be understood as a source of waves.
As a simple example, when a coherent beam of light is incident on two very narrow slits, as shown in the figure below, the light that emerges from the slits can be approximated as two spatially-separated point sources of coherent, in-phase spherical light waves.
The Double-Slit Experiment was originally conducted by Thomas Young in 1801 to show that light does indeed behave like a wave. Just like water waves interacting with each other, as light travels through two slits, the crests and troughs of the light waves will interact with each other and produce an interference pattern on the screen behind the slits.
