Required Practical 2 - Interference Effects

What apparatus is needed for the double slit experiment?

Laser

Double slit

White screen

Meter rule

Describe a method to determine the wavelength of a laser using double slits.

1. Set up apparatus and turn off lights

2. Adjust so D = 0.5m measuring with a meter rule

3. Measure 10 fringes using a meter rule and divide by number of fringes to find w

4. Increase D by 0.1m each time and repeat, up to 1.5m 

5. Repeat 2x more and find a mean w for each D 

6. Measure slit separation with vernier callipers

What graph should be plotted for young’s double slit experiment?

w agaisnt D

How can the wavelength of the laser be determined from the graph of w against D?

w = wavelength x D / s

wavelength = w x s / D = s x gradient

What safety precaution should be taken when carrying out young’s double slit experiment

Don’t shine the laser into people’s eyes/ don’t stand in front of a working laser

What improvements can be made to young’s double-slit experiment?

Ensure the screen and slit are lined up normally to the laser (use a set square)

What equipment is needed for a diffraction grating experiment?

Laser

Diffraction grating

White screen

Metre rule 

Describe a simple method for a diffraction grating experiment.

1. Set up apparatus and turn off lights

2. Adjust so D = 1m using a meter rule 

3. Measure the distances on each side of the central maximum and find the mean 

How is the slit separation found from the diffraction grating? 

Find the reciprocal of the number of slits per metre