Physics NYC (0.1-0.2-0.8) Interference and Diffraction Patterns Objective: To investigate the interference and diffraction of light Theory: Double-Slit Interference Interference maxima in a double-slit experiment are given by dy / L = m) (m =0, +1, +2, +3, ... ) Where d is the separation between the two slits, y is the position of the maximum on the screen measured from the center of the fringe, L is the distance from the slits to the screen and A is the wavelength of the light. It can be shown that the spacing between two adjacent maxima is ov = ym+1 -Vm = AL/d Single Slit Diffraction Diffraction minima from a single slit are given by ay / L = MX (M=+1, +2, +3, ...) Where a is the slit width. (Note that M + 0).Procedure Place the slide containing slits at least 2.5 m from the screen. Shine the laser perpendicular to the slits. Measure the distance L three times. For single slit diffraction experiments, use a ruler to measure the distance, AY, between the center of the first diffraction minimum on the right and the center of the first diffraction minimum on the left. The first diffraction minimum is determined by y = AY/2= Repeat the measurement three times. 1. 9 mm -> 0.9 cm = 0.9/2=0.45 cm 2. 1.0 cm = 1.0/2= 0.50 cm 3. 8 mm -> 0.8 cm = 0.8/2=0.40 cm Average = 0.45+ 0.50 +0.40/3 = 0.45 cm D=1.20 m =120 cm For doubleslit interference experiments, use a ruler to measure the distance, AY, between the right most maximum the left most maximum in the central diffraction region, and count the number of the maxima, n. The distance between the two adjacent maxima is then x = AY/ (111). Repeat the measurement three times. n=3 1. 1.1 cm = 1143-1) =1.1/2=0.55 cm 2. 1.0 cm =1.0/2=0.50 cm 3. 1.20 cm = 1.20/2=0.6 cm ANALYSIS: The wavelength of the HeliumNeon laser is 632.8 r1111. 1) For the singleslit diffraction experiment, calculate the slit width, a. Calculate its average and estimate the uncertainty. mtsmtheta) m A = dsin(theta) Y average = 0.45 cm Arctan (045/ 120) = x deg = 0.215 deg 632.8 nm = 6.328x10 7" A/ sin(theta) = wavelength laser = 6.328x10 7/g0215) = D=1.20m 2) For the doubleslit interference experiment, calculate the separation between the two slits, (1. Calculate its average and estimate the uncertainty. CONCLUSION AND DISCUSSION: 1) 'What are the slit width and the slit separation and their uncertainties