Ray Says That Interference Effects Cannot Be Observed with Visible

question 6

Multiple Choice

Ray says that interference effects cannot be observed with visible light because random phase changes occur in time intervals less than a nanosecond. Stacy says that doesn't matter if collimated light from a single source reaches multiple openings. (They are arguing about a light source 50.0 cm away from two 0.010 0 mm-wide slits, 2.00 mm apart, with a screen 1.00 m away from the slits.) Which one, if either, is correct, and why?

• A) Ray, because the phases at the two slits will be random and different.
• B) Ray, because it takes light over 3 ns to travel 1.00 m to the screen.
• C) Stacy, because the difference in time of travel from the source to the slits is no more than about 7 × 10−¹² s.
• D) Stacy, but only if a lens is placed in front of the slits.
• E) Both, because interference of light never occurs outside a physics lab.

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