🤓 Based on our data, we think this question is relevant for Professor Tsai's class at UCSD.

Both the double-slit interference pattern and single-slit diffraction patterns are observable. A diffraction pattern is formed in a double-slit when the slits are wide enough.

Single-slit diffraction,

$\overline{){\mathbf{a}}{\mathbf{}}{\mathbf{s}}{\mathbf{i}}{\mathbf{n}}{\mathbf{}}{\mathbf{\theta}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{\mathbf{n}}{\mathbf{\lambda}}}$

Double-slit interference pattern (maxima condition),

$\overline{){\mathbf{d}}{\mathbf{}}{\mathbf{s}}{\mathbf{i}}{\mathbf{n}}{\mathbf{}}{\mathbf{\theta}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{\mathbf{m}}{\mathbf{\lambda}}}$

where, a = slit width and d = slit's separation distance.

Draw the pattern you observed on the screen for the red laser. Which aspect of your drawing is due to double-slit interference, and which is due to single-slit? How can you tell? Indicate these on your drawing.

What happens to the pattern when you:

a. Increase the wavelength (What happen for double-slit pattern and single-slit pattern ?)

b. Slits are moved closer (What happen for double-slit pattern ?)

c. Each slit is widened (What happen for single-slit pattern?)