1. Click Start
2. Change the index of refraction and observe the speed of the wave in the second medium

How does an increase in the index of refraction change the speed of the wave travel?

Wavelength and speed changes, but not frequency. How can you see that the frequency doesn't change?

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                         Angle of incidence is not 90°                                                         Angle of incidence is 90°

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                              Explanation                                                                         In glass fiber

                           In water

Hard boundary (phase shift 180°)                                        Soft boundary (no phase shift)

                         Around an obstacle                        Through a small slit.                   Through a circular aperture

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               Pulses in opposite direction               Constructive and destructive interference           Superposition on a slinky

           .    

The purple wave shows the sum of the red and the blue waves.

1. Move the slider to change the position of the two speakers.
2. What is the distance between the speakers when the purple wave is the largest? (constructive interference)
3. What is the distance between the speakers when the purple wave is the smallest? (destructive interference)

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1. Choose: Interference
2. Set Frequency = max, amplitude = max, separation = 300, source = sound (the speaker)
3. Turn on both speakers

A) What kind of pattern do you observe? What is this pattern called?

B) Choose the pressure sensor on the right and move it to the right side of the box. Only use one of the sensors. Move it vertically on the right side of the screen.

1. Where do you have maximum pressure fluctuations?
2. Where do you have minimum pressure fluctuations?
3. A person moves along that vertical path. Describe what the person experiences as it moves from the bottom up to the top.

C) Click "both" at the bottom right. Where do you have maximum compressions? Where do you have maximum rarefactions?

Choose Example: Two Sources, Waves = Sound, Colour Scheme: Your choice, Source frequency = 6

Although the source is sound, think of these waves as water waves. It gives you the same pattern.

1. What pattern emerges? What is it called?
2. What do different colors represent?
3. Choose 3D view. What do you now observe?

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Non coherent light will not form any pattern. The changes are too fast for the eye to observe.                          Coherent waves create a pattern on the screen

Set the following values: wavelength = 4, L = 100, and d = 20. Do not change these values. 

• Change the position of Ym and see what happens to the path difference

1. Start from Y = 0. What is the path difference? Are the waves in phase or out of phase?
2. Keep increasing Y until the waves are perfectly out of phase - what is the path difference?
3. Keep increasing Y until the waves are perfectly in phase - what is the path difference?
4. Keep increasing Y until the waves are perfectly out of phase again - what is the path difference?
5. What do you think points 1 - 4 represent on the laser shone on the wall through the double-slit?

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Link here. (if simulation not working)

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1. Start the animation
2. Increase the amplitude so you see a difference in the movement of the orange and purple ball.- why is the purple ball not moving?
3. What happens to the position of the "still" place (purple) and "bumpy" place (orange) when you increase the distance between the sources - why?

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1. Click start
2. Observe the pattern that is being created.
3. What happens to the pattern if you decrease the wavelength? - Why"
4. What happens to the pattern if you decrease the distance between the two sources (d)?

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nλ = d sinθ

1. Click "Grating in Place"
2. What happens to the separation of the fringes when you increase the wavelength?
3. What happens to the separation of the fringes when you increase lines/mm (decrease the distance, d, between them)? 
4. Will you have an infinite or finite number of fringes on the screen?

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