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Two sources of light waves of equal frequency and amplitude are shown. The magnitude of the electric field is represented by the light and dark areas. The lighter the spot, the greater the magnitude of the electric field at that spot (position is given in nanometers). Restart.

1. Are the sources in phase or out of phase?
2. In terms of the wavelength of the light produced by the sources, is the distance between the sources 0.5 wavelength, 1 wavelength, 1.25 wavelengths, 1.5 wavelengths, 1.75 wavelengths, or 2 wavelengths? Explain.
3. If the wavelengths of both sources were halved, would point A remain a point of complete destructive interference, change to a point of maximally constructive interference, or be somewhere in between? Would point B remain a point of maximally constructive interference? If not, how would point B change? Finally, would point C remain a point of complete destructive interference? If not, how would point C change?

This applet calculates seven frames and then runs continuously. For a large number of sources, or for very small wavelengths, this calculation can take some time, so let the applet finish calculating all seven frames.

Problem authored by Melissa Dancy.