The center spot of Newton's rings is dark.This destructive interference occurs because:
A)the two beams travel distances that are different by half a wavelength.
B)both waves change phase by 180 $\degree$ as they are reflected.
C)one beam changes phase by 180 $\degree$ when it is reflected.
D)both waves have a trough.

Question

Quizplus · Accepted Answer

When light reflects off a medium with a higher refractive index, it undergoes a phase change of 180 degrees (half a wavelength). In Newton's rings, the light reflecting off the top surface of the air film does not undergo a phase change, while the light reflecting off the bottom surface (glass) does, leading to destructive interference at the center.

The Center Spot of Newton's Rings Is Dark °\degree° As They Are Reflected

The Center Spot of Newton's Rings Is Dark $\degree$ As They Are Reflected