WaveInterference
https://phet.colorado.edu/sims/html/wave-interference/latest/wave-interference_en.html
In your lab report, be sure to show calculations. Andinclude screenshots.
Part 1. Double Slit Interference In the pictures on the last page, the rays are emitted in all directions from the slits, but let’s concentrate on the rays that are emitted in a direction toward a distant screen (measuredfrom the normal to the barrier). One ofthese rays has further to travel to reach the screen, and the path difference is given by sind.Small anglesimplification: If is small(<< 1 rad), then sin (in radians), and bright spots occur on the screen at dm=; dark spots occur at ()dm21+=. As shown below, the angle (measured from the center of the screen) is related to the distance x measured on the screen by tan()=x/L, where L is the distance from the screen to the source of light (the aperture).laseraperturescreenL=x/LtanxIf the angle is small (less than a few degrees), then to an excellent approximation, sin() tan() (in radians) so the locations of the interference bright spots are given by dmLx==.Procedures:A)Setthe slit width to 500 nm and slit separation to 1500 nm. Record your slit separation din Table 1.
B)Press the green button on the light generator and generate an interference pattern on the screen. (Again,you should see something like what you see at the top of this page.)
C)Pull the measuring tape tool out of the box in the upper right and use it to measure L(using 3500 nmto 4000 nm), the distance between the slits and the screen. Then measure xthe distance from the center of the central bright spot to the center of one of the 1storder bright spots. Record these values in Table 1. (Be sure to include units!!!)
D)Calculate the wavelength of the light λusing the diffraction formula derived in the Background section. Record this value in Table 1.
E)Pause the simulation and use the measuring tape tool to measure the wavelength directly. Record this value in Table
1.
F)Calculate the %-error between your calculated and measured values, and record this value in Table
1. G)Adjust the frequency of light and repeatsteps B-F. Color of Light Slit Separation d Distance from Slits to Screen L Distance from Central to 1stOrder Bright Spot x Wavelength λ(calculated) Wavelength λ(measured) %-Error Red Violet Analysis:
1.What happened to the spacing of the bright spots when you increased the wavelength of the light?
2.Explain why your answer to #1occurred.
3.What happens to the interference pattern if d is increased? What if d is decreased?
4. Explain your reasoningfor 3.Insert screenshots here to prove your point.
5. Name one of the Applications. List the source of information.
Part 2. Single Slit DiffractionIf the viewing screen is far away, the rays heading for any point on the screen are essentially parallel.
Consider the waves emanating from the upper half and lower half of the slit. Destructive interference, a dark fringe, occurs if the path difference from any point in the upper half of slit and the corresponding points in the lower half of the slit is an integer multiple of λ/2so that the total electric field is zero.
The angle at which this occurs can be seen from the diagram to beD sinθ=λ[first minimum]The intensity is a maximum at θ= 0and decreasesto zero at the angle given byequation
(3).At a larger angle there will be a bright line, but not nearly as bright as the central spot at θ=0. As the path difference becomes an integer multiple of λ/2, there will again be a minimum of zero intensity whenD sin θm=mλProcedures:A)Setthe slit width to 1600nm.B)Press the green button on the light generator and generate an interference pattern on the screen.)
C)Pull the measuring tape tool out of the box in the upper right and use it to measure L(using 3500 nmto 4000 nm), the distance between the slits and the screen. Then measure xthe distance from the center of the central bright spot to the 1stdarkspots. Record these values in Table
1. (Be sure to include units!!!) D)Calculate the wavelength of the light λusing the diffraction formula derived in the Background section. Record this value in Table 1. E)Pause the simulation and use the measuring tape tool to measure the wavelength directly. Record this value in Table 1. F)Calculate the %-error between your calculated and measured values, and record this value in Table
G)Adjust the frequency of light and repeat steps B-F. Color of Light Slit widthDDistance from Slits to Screen L Distance from Central to 1stDarkSpot x Wavelength λ(calculated)Wavelength λ(measured) %-Error Red Violet Analysis:
1.What happened to the patterns when you increased the wavelength of the light?
2. Explain why your answer to #1occurred.
3.What happens to the diffraction pattern if d is increased? What if d is decreased?
4. Explain your reasoningfor 3.Insert screenshots here to prove your point.5. Name one of effects of diffraction seen in every day of life.