Waves

Question 1

What is a progressive wave?

Answer 1

A wave that transfers energy from a source through the surroundings by means of oscillations.

Question 2

What is a transverse wave?

Answer 2

A wave where vibrations are at 90 degrees to the direction of energy transfer.

Question 3

What is displacement of a wave?

Answer 3

The distance of a point on a wave above or below the mean position at any time.

Question 4

What is amplitude?

Answer 4

The maximum displacement of the wave from the mean position.

Question 5

What is wavelength?

Answer 5

The distance between two adjacent points in phase.

Question 6

What is a longitudinal wave?

Answer 6

A wave where vibrations are parallel to the direction of energy transfer.

Question 7

What is time period?

Answer 7

The time taken for one complete oscillation or wavelength.

Question 8

What is frequency?

Answer 8

The number of wavelengths per unit time.

Question 9

What wave phenomena can transverse waves experience?

Answer 9

Reflection, refraction, diffraction, interference, polarisation

Question 10

What wave phenomena can longitudinal waves experience?

Answer 10

Reflection, refraction, diffraction, interference

Question 11

What is phase difference?

Answer 11

How much one wave lags behind another as an angle in degrees or radians.

Question 12

What is the definition of intensity for a progressive wave?

Answer 12

The radiant power passing through a surface per unit area.

Question 13

What 2 things is intensity proportional to?

Answer 13

1 / distance from the source^2
Amplitude^2

Question 14

What is the order of waves from biggest to smallest?

Answer 14

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays

Question 15

What is diffraction?

Answer 15

When waves pass through a gap or around an obstacle and spread out into the space beyond.

Question 16

When does maximum diffraction occur?

Answer 16

When the wavelength of the source is equal to the gap through which it is diffracting.

Question 17

What is polarised light?

Answer 17

Light waves in which the vibrations occur in a single plane at 90 degrees to the direction of wave energy transfer.

Question 18

What is refraction?

Answer 18

The change in speed of a wave when it passes from one medium to another. There is usually a change in direction as well.

Question 19

What is the definition of refractive index?

Answer 19

The ratio of the speed of light in a vacuum to the speed of light in a medium.

Question 20

What happens to a ray of light when it moves from a less dense to a more dense medium?

Answer 20

The ray of light is refracted towards the normal so the angle of incidence > the angle of refraction.
The ray of light slows down in the denser medium and its wavelength decreases because its frequency stays the same.

Question 21

What things must be true for total internal reflection to take place?

Answer 21

The ray of light is travelling from a more dense to a less dense medium, the ray of light speeds up and bends away from the normal, the angle of incidence > critical angle.

Question 22

What is the definition of a critical angle?

Answer 22

When the angle of incidence is C, the angle of reflection is 90 degrees.

Question 23

What is total internal reflection?

Answer 23

When the angle of incidence is greater than the critical angle then all the light reflects at the boundary.

Question 24

What is the principle of superposition?

Answer 24

When two similar types of waves meet at a point, the sum of their individual displacements is equal to the displacement of the resultant wave.

Question 25

What is path difference?

Answer 25

The difference in distance from one source to the detector compared with the other source to the detector.

Question 26

What is interference?

Answer 26

Superposition of two progressive waves from coherent sources to produce a resultant wave with displacement equal to the sum of the individual displacements of the two waves.

Question 27

What is coherence?

Answer 27

When two waves are emitted with a constant phase difference, same frequency, polarised in the same plane and similar amplitude.

Question 28

What is destructive interference?

Answer 28

When two waves meet exactly in antiphase, the amplitudes cancel to produce no peaks or troughs.

Question 29

What is constructive interference?

Answer 29

When two waves meet exactly in phase, the amplitudes add up to produce large peaks and troughs.

Question 30

What does each symbol represent in the equation λ=ax/D

Answer 30

λ - wavelength a - slit separation x - fringe separation which is the distance between 2 adjacent bright fringes. D - distance between the slits and screen

Question 31

What must be true for λ=ax/D to be useable?

Answer 31

a must be much smaller than D (a<

Question 32

How are standing waves produced?

Answer 32

As a result of superposition of two progressive waves with the same amplitude and frequency, travelling at the same speed but in opposite directions meet and undergo superposition producing nodes and antinodes.

Question 33

What is an antinode?

Answer 33

Where two waves interfere constructively and produce a wave of maximum amplitude.

Question 34

What is a node?

Answer 34

Where two waves interfere destructively and produce a wave with zero displacement.

Question 35

What is the distance between two adjacent nodes or two adjacent antinodes?

Answer 35

λ/2

Question 36

What is the distance between a node and antinode?

Answer 36

λ/4

Question 37

How does energy transfer in progressive waves differ to in standing waves?

Answer 37

In progressive waves energy is transferred in the direction of the wave. In standing waves energy is trapped between the source and reflector.

Question 38

How does wavelength in progressive waves differ to in standing waves?

Answer 38

In progressive waves wavelength is the minimum distance between two adjacent points oscillating in phase. In standing waves wavelength is twice the distance between adjacent nodes.

Question 39

How does phase difference in progressive waves differ to in standing waves?

Answer 39

In progressive waves phase changes across the complete cycle of the wave. In a standing wave between two adjacent nodes all particles are in phase. On the opposite side of the node all particles are in antiphase.

Question 40

How does amplitude in progressive waves differ to in standing waves?

Answer 40

In progressive waves amplitude is the same for all particles. In standing waves amplitude varies from zero at the nodes to maximum at the antinodes.

Question 41

What is monochromatic light?

Answer 41

Monochromatic is light with a single wavelength or frequency.

Question 42

What are harmonics?

Answer 42

Certain frequencies where standing waves are set up. Harmonics are whole number multiples of the fundamental frequency.

Question 43

What is the equation for path difference?

Answer 43

S1P -S2P

Question 44

How would you measure the slit separation?

Answer 44

Use a travelling microscope