Question: Wave Interference lab Go to HYPERLINK \"http://phet... Bookmarked Wave

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Question: Wave Interference lab Go to HYPERLINK "http://phet... Bookmarked Wave Interference lab Go to HYPERLINK "http://phet.colorado.edu/simulations/sims.php?sim=Wave_Interference" and click on Run Now. Introduction: When waves momentarily overlap, they temporarily add their amplitudes without affecting the original waves. Thisinterference can be seen when two wave sources are used and their overlaps viewed. You will view this phenomenon in parts I and II of this lab. When a wave strikes a barrier, some of the energy will bend around the barrier and spread out. This is known asdiffraction. In part three of the lab, you will view the results of splitting a single wave source with a narrow slit, and then observe as the new waves created at the slit interfere. The interference pattern that results is symmetrical. The bands of constructive interference are referred to as maxima (single=maximum). Important Formulas: Please note that many texts use n to represent the nth maximum from the central maximum. The College Board has chosen to use m, I suspect so as not to be confused with index of refraction. Procedure: PheT Simulations ? Play With Sims ? Sound and Waves ? Wave Interference Part I: Water Waves Analogy take some time to familiarize yourself with the simulations controls Observe the water waves created in the faucet analogy. The darker areas are areas of higher amplitude. Adjust frequency and amplitude and observe the characteristics of the waves. Comment on the waves as amplitude is changed: ________________________________________________________ Comment on the waves as frequency is changed: ________________________________________________________ Now add a second drip to the simulation. Observe the interference of the two water waves. Comment on the interference of the two waves: _________________________________________________________ Part II: Light Wave Interference Please note the waves take some time to settle out and show good graphs-be patient Change the simulation to show extremely-slowed light emission from the single-light source. Observe the wavelength of red light and then move the wavelength slider to cyan or blue light. Comment on the actual wavelength of blue light versus red light. Add the screen to show how the light would look if viewed on a screen Add a second light source and view the interfering waves and the pattern they create on the screen. Showing the Intensity Graph quantifies the energy that is incident upon the screen. What effect does amplitude have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does source spacing have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does wavelength have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ Part III: Light Wave Diffraction Reset the light waves simulation and show the screen and graph. Add a 2-slit barrier to the simulation and allow the graphs to be formed. Observe the interference pattern created when the characteristics of the simulation are adjusted. You may have to adjust amplitude when other elements of the simulation are changed to observe the graph. What effect does a larger amplitude have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does a shorter wavelength have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does a larger barrier-to-screen distance have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does a smaller slit width have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ What effect does a smaller slit separation have on the maxima separation in the interference pattern? __________________________________________________________________________________________________ Conclusion Questions and Calculations: You may check your approximate answers in the simulation Why would a helicopter passing over or near a TV antenna cause a garbled or unusable TV signal? __________________________________________________________________________________________________ The simulation uses monochromatic light. If white light was used instead, what would be seen on the screen? __________________________________________________________________________________________________ As wavelength of the incident light increases (blue?red) the maxima separation increases / decreases. Two thin slits with separation of .0250mm are placed over monochromatic orange laser light at 610.nm. What is the small angle measurement from the central maximum (zero degrees, inline with the source) to the first maximum? __________________________ A beam of green light is split by thin double slit with separation of 0.0500mm and incident upon a screen some distance away. The angles of the first and second maximums are .584o and 1.17o respectively. What is the wavelength of the green light? __________________________ A single, monochromatic indigo light source is shined through an etched, flat prism with a slit separation of .0250mm. The resulting interference pattern is viewed on a screen 1.25m away. The third maximum is found to be 6.6cm from the central maximum. What is the wavelength of the indigo light? __________________________ Where are the first and second maxima? __________________________ and __________________________ When the two additive colors blue (475 nm) and green (510 nm) are incident in equal magnitudes upon a white screen, the subtractive color cyan results. Consider two beams, one blue and one green. The blue beam is shined through a double-slit diffraction grating with slit distance of 0.0400 mm and then displays an interference pattern on a screen 1.00m away. If the green beam is then shined from the same position as the blue beam, what size diffraction grating would be required for the green beam so only a cyan interference pattern would be seen on the screen? _____________

Explanation / Answer

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Part I: Interferrence and

Part II Diffraction

1. When waves as amplitude is changed, the interference will have sum of their amplitude as when in phase or zero when in opposite phase.

2. When waves as frequency is changed: it will have new frequency f = ½(f1 + f2 ) and f = ½(f1 - f2) (generation of beets)

3. What effect does amplitude have on the maxima separation in the interference pattern?

Since the wavelength are different, frequency will be different and depends on the beat frequency and it ia 1/2 of difference in frequency.or average frequency. Amlitude will ne sum of it or zero but separated by beat frequency.

4.  What effect does source spacing have on the maxima separation in the interference pattern?

spacing less more interfernce as more wavefront.

5. What effect does wavelength have on the maxima separation in the interference pattern?

wave length is small, more wave front more interference less separation.

6.What effect does a larger amplitude have on the maxima separation in the interference pattern? (double single slit)

No effect.

7.What effect does a shorter wavelength have on the maxima separation in the interference pattern?

less separation

8.What effect does a larger barrier-to-screen distance have on the maxima separation in the interference pattern?

if screen distance more than barrier separation will be more otherwise less

9.You may check your approximate answers in the simulation Why would a helicopter passing over or near a TV antenna cause a garbled or unusable TV signal?

Destrctive patteren.

10.The simulation uses monochromatic light. If white light was used instead, what would be seen on the screen?

White light

11.As wavelength of the incident light increases (blue?red) the maxima separation increases / decreases

decreases.

12. wo thin slits with separation of .0250mm are placed over monochromatic orange laser light at 610.nm. What is the small angle measurement from the central maximum (zero degrees, inline with the source) to the first maximum?

0.0244 degree

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