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In light diffraction, if blue light is substituted for red light, what happens to the fringe pattern?

1. The fringes become closer together
2. The fringes spread farther apart
3. The fringe spacing remains unchanged
4. None of the above

Correct answer: The fringes become closer together

Solution

Fringe spacing beta = lambda*D/d is proportional to wavelength. Blue light has a shorter wavelength than red, so the fringes move closer together.

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