Double-Slit Experiment Simulator
Classroom worksheet · Interactive simulation: https://lkforge.com/tools/physics/double-slit-experiment/
Name: Date:
Learning objectives
- Explain interference of waves passing through two slits.
- Relate fringe spacing to wavelength, slit separation, and screen distance.
- Connect the pattern to the wave nature of light.
Variables to change
- Wavelength
- Slit separation
- Screen distance
Procedure
- Set a mid-range wavelength and note the bright-fringe spacing on the screen.
- Increase the wavelength and observe how the fringe spacing changes.
- Increase the slit separation and observe the fringe spacing again.
Observations
Record the bright-fringe spacing as you vary wavelength and slit separation.
Questions
- What causes the bright and dark fringes?
- How does increasing the wavelength affect fringe spacing?
- How does increasing the slit separation affect fringe spacing?
- Write the condition for bright fringes.
- What does this experiment demonstrate about the nature of light?
Answer key (instructors)
- 1. Constructive interference (path difference = whole number of wavelengths) makes bright fringes; destructive interference (half-wavelength differences) makes dark fringes.
- 2. Fringe spacing increases — spacing is proportional to wavelength.
- 3. Fringe spacing decreases — spacing is inversely proportional to slit separation.
- 4. d·sinθ = mλ, where m = 0, 1, 2, … and d is the slit separation.
- 5. That light behaves as a wave; the interference pattern cannot be explained by particles alone.
Light from two slits overlaps and interferes. Where crests meet crests the screen is bright; where crests meet troughs it is dark. Fringe spacing grows with wavelength and shrinks with slit separation, per d·sinθ = mλ — direct evidence of light’s wave nature.