Two waves with the same frequency
have a phase difference of zero degrees. Which of the following is the
interference produced by the waves? (A) Constructive interference, (B)
destructive interference, (C) neither constructive nor destructive interference.
Here, this question is asking us
what kind of interference would be produced if two light waves with the same
frequency and with a phase difference of zero degrees were to interact with each
other. Notice that we’re told that the two
waves have the same frequency, which means their phase difference will stay constant
as they travel. Recall that when two light waves
occupy the same space at the same time, they will interfere with each other. This interference can be either
constructive or destructive. Let’s look closer at what causes
light waves to produce constructive interference and destructive interference.
Constructive interference occurs
when the peaks and troughs of two waves line up with each other, with the resultant
wave having an amplitude that is the original waves amplitudes combined. Destructive interference, on the
other hand, occurs when the peaks of one wave line up with the troughs of the second
wave. The amplitudes of the two waves
will cancel each other out and leave us with a resultant wave that has an amplitude
With both constructive and
destructive interference, the resulting wave’s amplitude will be the sum of the
amplitudes of the original waves. One important term to think about
here is phase difference, which is the number of degrees that separate two
waves. In this table, we can see various
phase differences and how the two waves line up with them, resulting in constructive
and destructive interference. Where there are zero degrees of
phase difference, the waves constructively interfere. And where the peaks are furthest
apart at 180 degrees, destructive interference will occur, producing a resultant
wave with an amplitude of zero.
This question asked us what kind of
interference would be produced when there is a phase difference of zero degrees. From the table, we know that the
maximum constructive interference occurs at zero degrees and 360 degrees. Therefore, the first option,
constructive interference, is the correct answer.