Two Slit Interference - Using a Digital SLR
The goal here is to use a digital SLR to extract quantitative spatial and intensity information for experiments in optics for undergraduate level physics courses. Here I used a PASCO (8528) diode laser (670 nm nominal), a two-slit interference pattern (slit width = 0.04 mm and separation = 0.25 mm) and projected the pattern on a ground glass screen. The setup and interference pattern are shown below.
I used a Nikon D300s with a 105mm lens mounted on a tripod, looking at the back side of the ground glass screen (about 4 cm wide). The pattern on the ground glass screen was 3.5 cm and occupied about 60% of the width of the camera's CCD. I used the image processing tools of IGOR Pro to extract quantitative information about the intensity pattern.
The above plot shows the intensity data (in red) and the curve is the expected intensity pattern folding in diffraction, due to the slit width (a ), and interference, due to slit separation (b). The formula is given below. N is an arbitrary normalization, lambda is the wavelength and L the slit-to-screen distance. The intereference part agrees to within 4% of the numbers quoted in the setup figure while the diffraction envelope agrees to within 10%