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?)

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Single Slit Diffraction concept. You can view video lessons to learn Single Slit Diffraction. Or if you need more Single Slit Diffraction practice, you can also practice Single Slit Diffraction practice problems.

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