Chapter 12: Waves 2

Question 1

What is superposition?

Answer 1

Superposition is when two waves superpose, or overlap at a point in space, creating a resultant wave where the displacement is equal to the total displacement of the two overlapping waves at that point.

Question 2

What is the principle of superposition?

Answer 2

The principle of superposition states that when two waves meet at a point, the resultant displacement at that point is equal to the sum of the individual displacements at that point.

Question 3

What is interference?

Answer 3

Interference is the overlapping of two waves from two coherent sources to produce a wave where the displacement at the resultant wave is equal to the sum of the displacements of the two individual waves.

Question 4

What is constructive interference?

Answer 4

Constructive interference is when two in phase waves superpose creating a resultant wave with a greater amplitude than the original waves.

Question 5

What is destructive interference?

Answer 5

Destructive interference is when two waves in anti-phase overlap and cancel out creating a resultant wave where the amplitude is smaller than the original waves.

Question 6

What is meant by coherence?

Answer 6

Coherence is when two separate sources produce waves that have a constant phase difference between them, or two waves that have a constant phase difference between them.

Question 7

What is meant by path difference?

Answer 7

Path difference is the fraction of a wavelength where one point is behind another. Expressed in m or cm.

Question 8

What is meant by phase difference?

Answer 8

Phase difference is the fraction of a wave cycle by which one point is behind another. Expressed in degrees or radians.

Question 9

What are stationary waves?

Answer 9

Stationary waves are waves that remain in a constant position with no net energy transfer and consists of nodes and antinodes,

Question 10

How are stationary waves created?

Answer 10

Stationary waves are created when two waves of the same frequency and similar amplitude superpose.

Question 11

What are nodes and antinodes?

Answer 11

On a stationary wave, nodes are points on a stationary wave where the displacement is always zero. Antinodes are points on a stationary wave with maximum amplitude and intensity.

Question 12

What is a fundamental frequency?

Answer 12

Fundamental Frequency is the minimum frequency needed for an object to vibrate.

Question 13

What is the fundamental mode of vibration?

Answer 13

The fundamental mode of vibration is a vibration at the fundamental frequency.

Question 14

How does the speed of the wave change when a string vibrates on a string with fixed tension?

Answer 14

The speed of the wave on the string does not change. It remains constant.

Question 15

What is the length of the wave relative to a string for a vibration in the first harmonic?

Answer 15

For a string vibrating in the first harmonic, the wavelength is equal to two times that of the spring,

Question 16

How does the length of a wave on a spring change as the string vibrates at the next multiple of the fundamental frequency?

Answer 16

When the frequency increases by a multiple of the fundamental frequency, the wavelength would be 1L (or 2/2) for the second harmonic, 2/3L for the third, 2/4L, 2/5L and so on, or 2 over the multiple of the fundamental frequency.

Question 17

How will frequency change as you go onto the next harmonic?

Answer 17

As you move on to the next harmonic, the frequency will be equal to the fundamental frequency times the harmonic (or multiple) number.

Question 18

In a closed tube, what node would a closed and open end be?

Answer 18

In a closed tube, the closed end would act as a node, and an open end would act as an antinode.

Question 19

What is the length of the wave relative to the length of the tube in a closed-open tube at the first harmonic, and how will it change in greater harmonics?

Answer 19

For a closed-open tube at the first harmonic, the tube would be 1/4 of the length of the wave, or 1/4λ, and increase by 1/2 after every harmonic. Eg: 2nd Harmonic is 3/4λ, 3rd Harmonic is 5/4λ , 4th Harmonic is 7/4λ etc.

Question 20

What is the length of the wave relative to the length of a tube for a tube with two open ends?

Answer 20

For a tube with two open ends, the tube would be equal to 1/2 of the length of the wave (1/2λ), and increase by 1/2 after every harmonic. Eg: 2nd Harmonic: 1λ, 3rd Harmonic, 3/2λ, 4th Harmonic: 4/2λ etc.