RP2-Interference

• Double slit equipment: laser, double slit, white screen, ruler.
• Double slit set up: The laser should be positioned so it shines through both slits on the double slit (using a single slit if necessary) and then onto the white screen. The room should be darkened.
• Double slit method: Measure the distance D between the double slit and the screen, and the slit separation s. Measure a large number of fringes on the screen and divide by the number of fringes to get fringe separation w. Increase D and repeat.
• Double slit graph: Plot a graph of w against D. The gradient is wavelength divided by slit seperation.
• Double slit analysis: The wavelength of the laser can be found by multiplying the gradient by slit separation.
• Double slit safety: Keep lasers away from eyes.
• Diffraction grating equipment: Laser, diffraction grating, white screen, ruler.
• Diffraction grating set up: The laser should be positioned so it shines through the diffraction grating and then onto the white screen. The room should be darkened.
• Diffraction grating method: Measure the distance between the diffraction grating and the screen and between the central maxima and the first order maxima and the central maxima and the second order maxima.
• Diffraction grating analysis: Find the slit separation d of the diffraction grating by doing 1/slits per metre (N). Find the angular separation by doing arctan (distance between fringe and central fringe/distance between screen and diffraction grating). Wavelength is (slit separation x sin(angular separation)/order of maxima.
• Diffraction grating safety: Keep laser away from eyes.