. Go to http://phet.colorado.edu/en/simulation/legacy/wave-interference and clic
ID: 1529384 • Letter: #
Question
. Go to http://phet.colorado.edu/en/simulation/legacy/wave-interference and click ‘Run Now!’ to start the ‘Wave Interference’ simulation. Click on the ‘Light’ tab towards the upper left, then click the ‘Show Screen’ button on the right, then click the ‘Intensity Graph’ button that just appeared. This produces a picture of a viewing screen and a graph of the intensity of the light on that viewing screen. Describe your observation D2Is able to design a reliable experiment that solves the problem The experiment does not solve the problem. The experiment attempts to solve the problem but due to the nature of the design the data will not lead to a reliable solution. The experiment attempts to solve the problem but due to the nature of the design there is a moderate chance the data will not lead to a reliable solution. The experiment solves the problem and has a high likelihood of producing data that will lead to a reliable solution. 5 of the viewing screen and the graph. Note: The graph is not a straight line. The intensity of the light in the middle of the screen is slightly more than at the ends. Explain why this makes sense. It might not be clear at this point just what the simulation is showing you (what the ripples, the screen, or the graph represent). Click on the “Add Detector” button to add an electric field detector to the simulation. It will measure the electric field as a function of time at the location of the cross hairs. Note: You can pause/step through the simulation (buttons at the bottom) so that you can make careful observations.
a. Click on the radio button labeled ‘Two lights’. Set the spacing to one tick mark from the right. Describe in detail your observations of what happens to the screen, the graph, and the region between the lights and the screen.
b. Now turn off the top light and wait. What happens? Suggest an explanation for why the viewing screen and graph change so dramatically with one light on versus two.
c. Return to the ‘One light’ setting but shorten the wavelength of the light so that it is blue or violet. Also increase the amplitude to maximum. Describe your observations of the viewing screen and the graph.
d. Now switch to the two-light setup from #2 above. Describe in detail your observations of what happens to the screen, the graph, and the region between the lights and the screen. Describe how it is different from what you observed in #2.
e. Click “Reset All”, then ‘Show Screen’, then ‘Intensity Graph’. Increase the amplitude to maximum, and add ‘Two slits’. Set the slit width to halfway between the 2nd and 3rd tick marks from the left. Set the barrier location to the middle, and the slit separation to two ticks from the right, and wait. Record your observations of the viewing screen, the graph, and the region between the barrier and the screen.
f. What similarities do you notice between your observations of two light sources (#2) and a single light source with a barrier with two slits? Suggest an explanation for the similarities
Explanation / Answer
.In the intensity graph,the intensity is 0.25 for x<=0.2 and x>=0.8 and it is greater than 0.25 at 0.2<x<0.8.This is because at the central maximum wave interfere with zero phase difference or multiples of 2pi .Also intensity decreases as distance increases.a)Here two lights are used the pattern on the screen is due to superposition of two.At x=0.5,0.3,0.7 the intensity is maximum because the path difference is n lambda or phase difff is n(2pi)..At x=0.2,0.4,0.6,the intensity is minimum because the path differnce is (2n-1)lambda/2 or phase diff is (2n-1)pi.b)When one light is turned off there is no interference of light due to two light sources,the screen has pattern due to wavelets of second light.The intensity goes on decreasing as we go up.c)When only one light is used there is no interference of secondary wavelets due to another.d),Due to large no.of secondary wavelets the viewing screen are moving fast..The aintensity is high because amplitude is high.e) In the viewing screen periodic wavelets of red colour occur and spread.thay meet barrier.On the screen interference pattern due to waves from slits are formed which is dark along the length of barrier and bright other than that..The graoh shows high intensity after x=0.8and 0.2 and less intensity with alternate bright and dark fringes other than that.f)The intensity of graph from x=0.35 to 0.7 is alternate bright and dark fringes. The intensity of light is high for x>0.8 and x<0.2.
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