10. Superposition of 2-D Waves: Ripple Tank Simulation

This simulation shows a top view of a source (represented by the red dot) making waves on the surface of a tank of water (imagine tapping the surface of a pond with the end of a stick). The white circles coming from the spot represents the wave crests with troughs in between. Holding down the mouse in the simulation gives the x, y coordinates of the mouse which will allow you to locate maxima and minima in the simulation.


Note: This animation gets off to a slow start.

Questions:

10.1. Add a second source by clicking on the 'Two Sources' button. Waves from each source will cancel in some places (destructive interference) but add in other places (constructive interference).  How many lines of constructive interference do you see (not counting the ones going off directly to the left and right)?
Sources:
10.2. With two sources use the following buttons to change the wavelength of the sources. How many lines of destructive interference do you see in each case?
10.3. With two sources and a wavelength of 2.0, use the following buttons to change the distance between the sources. How many lines of destructive interference do you see in each case? Does more separation cause more or fewer spots?
10.4. Suppose instead of a ripple tank this simulation represented two light sources (which have the same wavelength and start off in phase- for example laser light from from a single source shining through two small openings). The light starts at the bottom of the simulation and reaches a screen (the green bar) at the top edge of the simulation. How many bright spots would be seen on the screen for the following case (assume the screen is big enough to show all the lines of constructive interference)?
Two Sources:
10.5. If the simulation represented a double slit light source, changing the wavelength would be equivalent to changing the color. Describe the difference in the location of the bright spots for the color represented by wavelength equal to 1 compared to the location of the spots for the color represented by wavelength equal to 2. Do they occur in the same location on the screen (at the top edge of the simulation)?

10.6. What would be the result on the screen of shining light which was a mixture of two colors through a double slit?

The formula for double slit interference is given by  for the case of constructive interference and  for desctructive interference. In both cases d is the distance between the center of the openings, the angle q is the angle from the central maximum out to a minimum or maximum and m numbers the maximums (or minimums) starting from the center (m = 0). NOTE: In order to actually measure this effect for light the slits must be very small and close together and the screen quite a distance away.
Credits.
Go To: IUS Physics Top Page.
Contact Dr. K. Forinash, for comments/suggestions/corrections.