Question

which statement describes an example of constructive interference?
a. a cell - phone signal is lost when you pass through a certain area.
b. oil spilled in a water puddle shows different colors of light.
c. light forms bars on a surface after passing through two slits.
d. two tv signals reach an antenna and cancel each other out.

Explanation:

• Option A: Signal loss is due to destructive interference (waves canceling each other), not constructive.
• Option B: Oil - water color display is due to thin - film interference (a type of interference, but not the classic constructive interference in the context of wave superposition for bright regions as in double - slit).
• Option C: In the double - slit experiment, when light passes through two slits, at the points where the path difference \(d\sin\theta = n\lambda\) (\(n = 0,1,2,\cdots\)), constructive interference occurs, and these points correspond to the bright bars (maxima) on the screen.
• Option D: Signals canceling each other out is destructive interference.

Answer:

C. Light forms bars on a surface after passing through two slits.