Question Video: Identifying the Nature of the Interference between Two Waves Interfering | Nagwa Question Video: Identifying the Nature of the Interference between Two Waves Interfering | Nagwa

# Question Video: Identifying the Nature of the Interference between Two Waves Interfering Physics • Second Year of Secondary School

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Two waves with the same frequency have a phase difference of 0°. Which of the following is the interference produced by the waves? [A] Constructive interference [B] Destructive interference [C] Neither constructive nor destructive interference

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### Video Transcript

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 of zero.

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.

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