lab6

Lab 6: Interference and Diffraction Introduction: Light passing through a single slit is called diffraction ; however light passing through the double slit is called interferenc. Addtionally, these pattern varies in different condition. Foe example, increasing or dreasing the slit width would affect both inteference, and diffraction pattern. Further more, decreasing the slit width in a single slit increases the width of the central maximum; however decreasing the slit width in a double slit would cause the maxima(m=5/m=10) will be further apart. Procedure: Part 1: The screen was covered with a piece of paper on the other side facing the laser. The slit was adujusted to appropriate slit width. The distance between the screen and the slit was measure. For this experiment a single slit was used. The diffraction pattern of the minima was marked on the paper, and the distance between first orders and second orders was recored. The same was repeated with various slit width, and calculations were made at the end. Part 2: The screen was covered with a piece of paper on the other side facing the laser. The slit was adujusted to appropriate slit width. The distance between the screen and the slit was measure. For this experiment a double slit was used. The interferance pattern of the maxima was marked on the paper, and the distance between the 5 th orders and 10 th orders was recored. The same was repeated with various slit width, and calculations were made at the end. Lastly, 0.04mm slit width and slit seperation of 0.50 mm was used to the maxima for the green laser. Results: Screen distance(D): 0.62 m(+- 0.0005m) Laser wavlength: 650 x10^-9m Table 1: Diffraction of a single slit Given slit width: agiven=0.00004m Given slit width: agiven=0.00016m Given slit width: agiven=0.00008m m=1 m=2 m=1 m=2 m=1 m=2

Distance between left and rigth minima(2y) (m) (+- 0.0005m) 0.0285 0.045 0.005 0.01 0.02 0.03 Mean distance between minma and center(y) (m) (+- 0.0005m) 0.01125 0.0225 0.0025 0.005 0.01 0.015 Calculate slit width (acal) (m) (+- 0.0005m) 3.58x10^-5 3.58x10^-5 1.612x10^-4 1.612x10^-4 4.03x10^-5 8.06x10^-5 Percent error acal, and agiven (%) 10.4 10.4 0.75 0.75 49.6 0.75 Given slit seperation: 0.005m Screen distance(D): 1.03m (+- 0.005m) Laser wavlength: 650x10^-9m Slit width=4x10^-5m Table 2: Intereferance of double slit (red laser) m=5 M=10 Distance between left and rigth minima(2y) (m) (+- 0.005m) 0.013 0.026 Mean distance between minma and center(y) (m) (+- 0.0005m) 0.0065 0.013 Calculate slit width (acal) (m) (+- 0.000005m) 5.15x10^-5 5.15x10^-5 Percent error acal, and agiven (%) 3 3 Given slit seperation: 0.005m Screen distance(D): 0.62m(+- 0.5m) Laser wavlength: 532x10^-9m Slit width=4x10^-5m Table 3: Intereferance of double slit (green laser)

Questions: Q1: Dark fringes on the screen on a single slit is caused by a destructive interference, and the bright fringes on the screen on a single slit caused by constructive interference. Q2:asintheta=mλ Q3:tan(theta)=y/D Q4 tan(theta)=y/D tan(theta)=0.01m/1m Theta=tan^-1(0.01m/1m)=0.57 Since theta is really small, it shouldn’t introduce significant amount of error. Q5:y=mλD/a a=mλD/y Q6: : This equation is really similar to the one describing diffraction because the condtions in a minima is same as the conditions in a maxima double slit Q7: asintheta=mλ Q8: :tan(theta)=y/D Q9:dcal= mλD/a Q10Q11: light fringes in a double slit is produced when two lights travel the same distance to the screen; however dark fringle in a double slit is produced by lights traveling out of phase(180 degreees). Q11: Changing the slit width will affect the difraction pattern, and it depends wheather the slit is widder or narrower. If the width is widder, the the diffraction pattern decreases(closer), and if the slit was narrower the diffraction pattern will increase. Increase in d=increase in sin(theta)=increase in theta Q12: If slit seperation increases, the inference pattern decreases, and the slit seperation is narrower the slit seperation increases Q13: If slit width increases, the inference pattern decreases, and the slit width is narrower the slit seperation increases Q14: Increase in waevelength= increase in interference pattern Decrease in waevelength= Decrease in interference pattern Q15: If young’s experiment was done under the water, the fringes are closely spread. Speed of the light decreases, so does the fringe with