Double slit experiment (4.2)

Question 1

Why do we use a laser for the double slit experiment?

Answer 1

Laser light is:

• coherent, so it can be used to for two coherent point sources using a double slit.
• Monochromatic, so only a single wavelength is present

Question 2

Why do the slits have to be about the same size as the wavelength of the laser?

Answer 2

It means the laser light is diffracted more, so it acts as two coherent point sources

Question 3

How do you measure fringe spacing?

Answer 3

Using a phone of course! No, digital calipers+paper. Its better to measure across several fringes and divide by the number of spacings between them to lower the percentage error