Wave Properties ( 2 )

Question 1

What is the super position effect?

Answer 1

• When waves meet, they pass through each other
• At the point where they meet, they combine for an instant before they move apart
• Combining effect is super position

Question 2

What happens when waves cross?

Answer 2

• Displacements due to each wave combine.

* Then each wave separates and continues their path

Question 3

What is the principle of superposition?

Answer 3

When two waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point

Question 4

What happens when a crest meets a crest?

Answer 4

A supercrest is created, two waves reinforce each other

Question 5

What happens when a trough meets a trough?

Answer 5

• Super trough is created

* Two waves reinforce each other

Question 6

What happens when a crest meets a trough of the same amplitude?

Answer 6

• When a crest meets a trough of the same amplitude, the resultant displacement is zero
• The two waves cancel each other out

Question 7

What is a minimum?

Answer 7

If a crest meets a trough that is not exactly the same amplitude, the resultant is called a minimum

Question 8

When are stationary waves formed?

Answer 8

When two waves are continuously sent from either end.

Question 9

What are progressive waves?

Answer 9

Two sets of waves, term is used in order to distinguish from stationary waves.

Question 10

What is constructive interference?

Answer 10

Two waves reinforce each other

Question 11

What is destructive interference?

Answer 11

Two waves cancel each other out

Question 12

What is a node?

Answer 12

Point of no displacement

Question 13

What is the phase at each node?

Answer 13

At each node along the stationary wave, the two sets of waves are always 180 degrees out of phase, so they cancel each other out.

Question 14

What is interference?

Answer 14

• As waves are continuously through each other at constant frequency and at constant phase difference, cancellation and reinforcement occurs at fixed position
• This is known as interference

Question 15

What interference pattern do coherent waves produce?

Answer 15

• Coherent sources of waves produce an interference pattern where they overlap
• Because they vibrate at the same time with a constant phase difference

Question 16

What happens if phase difference is changed at random?

Answer 16

• Points of cancellation and reinforcement would move about at random
• No interference pattern would be produced

Question 17

When are two points in phase?

Answer 17

• When they are both at the same point in the wave cycle
• Points in phase have the same displacement and velocity
–

Question 18

What is the phase difference of points in phase?

Answer 18

• Zero
or
• Multiple of 360 degrees ( full cycle )

Question 19

What is the phase difference of points not in phase?

Answer 19

• Odd number multiples of 180 degrees ( half cycles ) are exactly out of phase

Question 20

What is required to get clear interference patterns?

Answer 20

Two or more sources must be coherent and in phase

Question 21

When are two sources coherent?

Answer 21

• Same wavelength, frequency and a fixed phase difference between them