A Lab Report on Interference of Light
In the laboratory we explored light interference which included two slit interference and diffraction by a single slit by letting monochromatic, coherent light through different apertures and also by using a linear polarizer. The data used included bright spots(around maxima) and shadows (around minima) produced by different apertures, and the variation of the intensity of polarized light transmitted through a linear polarizer. The experiment had concern about the Fraunhofer case, when the observation of light is done at distances from the obstacle orders of magnitude larger than the aperture’s length scale. The detailed problem was treated by solving Maxwell’s equations with adequate boundary conditions representing the opaque parts of the aperture.
i)To confront the theory about interference developed in class quantitatively against experimental data .
ii)To approximate the light waves with Huygen’s principle.
MATERIALS AND EQUIPMENT
A laser diode of wavelength 650(10)nm.
A light sensor
i)DIFFRACTION AND INTERFERENCE
First record the distance Δfn from the maximum of intensity to the nth minimum after the maximum.
- Set up the apparatus so that the screen selector with the single slit is placed in the path of the laser beam.
- Place a quadrille ruled paper on the white screen at the end of the track and determine the distance D between the aperture and the screen.
- Project the light after the aperture selector onto the screen. You may have to adjust the light source and the aperture positions in order to produce a pattern aligned with the horizontal. For your first aperture, you may select one of the single slits. Choose one that maximizes your ability to discern the minima on the screen. Mark with a pencil on the paper the points where you believe are the minima of intensity. Mark as many as you can see. Mark as well the point of maximum intensity. Elaborate a method for the error estimation of the exact points of these marks.
- Remove the paper from the screen. Make sure you can identify the marked paper with the parameters used (wavelength, aperture length parameters, distance from the aperture to the screen)
- If instead of a single slit, you had a double slit with the same width, how would qualitatively the interference pattern be modified? Test your prediction by observing the pattern for one of the double slits, and repeat the procedure 1–4. Perform again the measurement for another double slit with the same width for the slits but different separation.