Question

A. Draw the wave that results when the two waves shown interact through destructive interference. (Image attached)

b. The sounds from a stage seem louder in certain seats in the auditorium. Write one or two sentences to explain the wave interaction that is responsible for these loud spots.

c. Write one or two sentences to define reflection and to describe a situation that demonstrates this wave interaction.

Answer 1

a) Since these waves are opposite, they will cancel one another (see fig.)

b) If we consider sound speakers, the waves may interfere and destruct each other (like on the attached figure), somewhere they will increase each other (constructive interference).

c) Echo. Go to mountains and scream (beware of avalanche), you'll wonder how many sound waves will come to you from different surfaces against you. This is used in echolocation.

Answer 2

PART A)

Since two waves are in opposite phase

So due to superposition of these type of opposite phase waves the resultant wave is of zero amplitude

This is known as destructive interference

PART B)

Sound from stage seem to be louder at certain seats because of constructive interference of sounds which are coming directly and coming after reflection from walls and other points

This superposition is the result where we get larger amplitude sue to superposition of same phase

PART C)

When a travelling wave bounce back in opposite direction by the change in medium boundary then this phenomenon is known as reflection of wave

If the reflected sound is in opposite phase then the superposition of such sound will give destructive interference

If reflected sound is in same phase then the resultant sounds is always constructive interference