Physlet Illustration: Single-Slit Diffraction

 

 
l = mm W = mm
In this simulation, waves in a ripple tank originate from a narrow slit, shown in red. You may vary both the wavelength and the slit width. The resulting interference may be observed in the ripples of the waves that propagate in the tank. Angles at which constructive interference occurs are characterized by alternating peak and troughs. Angles at which totally destructive interference occurs are characterized by an absence of such "ripples". At what angles do these interference phenomena occur?

Hints:

  1. Change the slit width. (0.1 mm < W < 0.3 mm) How does it affect the interference pattern?
  2. Change the wavelength. (0.1 mm < l < 0.5 mm) How does it affect the interference pattern?
  3. Can you find combinations of W and l for which no interference phenomena are observable? Why?
  4. Verify that there is always constructive interference at q = 0° (straight up).
  5. Destructive interference occurs at angles where the waves from regions within the slit are out of phase by 180°. What is the condition for this to occur?

Reference

See Walker, Section 28-4

Illustration written by Steve Mellema