4.4 Waves

Question 1

What is amplitude?

Answer 1

A wave’s maximum displacement from its equilibrium position.

Question 2

What are Antinodes?

Answer 2

A position of maximum displacement in a stationary wave.

Question 3

What is Coherence?

Answer 3

Waves with the same frequency and constant phase difference.

Question 4

What is Constructive Interference?

Answer 4

The type of interference that occurs when two waves meet in phase. The wave amplitudes are superposed.

Question 5

What is Critical Angle?

Answer 5

The angle of incidence that results in an angle of refraction of exactly 90°. It is when the refracted ray travels along the boundary line.

Question 6

What is Destructive Interference?

Answer 6

The type of interference that occurs when the two waves are in antiphase. When one wave is at a peak and one is at a trough their addition results in a minimum point.

Question 7

What is Diffraction?

Answer 7

The spreading of waves as they pass through a gap of a similar magnitude to their wavelength.

Question 8

What is Displacement?

Answer 8

The distance that a point on a wave is from its equilibrium position.

Question 9

What is the Electromagnetic Spectrum?

Answer 9

The spectrum of electromagnetic waves, consisting of Gamma Rays, X-Rays, Ultraviolet, Visible Light, Infrared, Microwaves and Radiowaves.

Question 10

What are Electromagnetic Waves?

Answer 10

Waves that consist of perpendicular electric and magnetic oscillations. All electromagnetic waves travel at the speed of light in a vacuum.

Question 11

What is Frequency?

Answer 11

The number of waves that pass a point in a unit time period. It is the inverse of the time period.

Question 12

What is the Fundamental Mode of Vibration?

Answer 12

The oscillation of a wave at its natural frequency.

Question 13

What is Intensity?

Answer 13

The power transferred per unit area. It is proportional to the square of a wave’s amplitude.

Question 14

What is interference?

Answer 14

The superposition of the amplitudes of waves when they meet.

Question 15

What are longitudinal waves?

Answer 15

A wave with oscillations that are parallel to the direction of energy propagation.

Sound waves are an example of a longitudinal wave. They cannot travel through a vacuum.

Question 16

What are nodes?

Answer 16

A position of minimum displacement in a stationary wave.

Question 17

What is an oscilloscope?

Answer 17

A device used to display and analyse waveforms.

Question 18

What is path difference?

Answer 18

A measure of how far ahead a wave is compared to another wave, usually expressed in terms of the wavelength.

Question 19

What is the period of a wave?

Answer 19

The time taken for a wave to complete one full cycle.

Question 20

What is phase difference?

Answer 20

The difference in phase between two points on a wave. It is usually expressed in radians.

Question 21

What is polarisation?

Answer 21

The restriction of a wave so that it can only oscillate in a single plane.

This can only occur for transverse waves.

Question 22

What are progressive waves?

Answer 22

Waves that transfer energy from one point to another without a transfer of matter.

Question 23

What is reflection?

Answer 23

The bouncing of a wave at a boundary. The angle of incidence will equal the angle of reflection.

Question 24

What is refraction?

Answer 24

The changing of speed of a wave as it passes into a new medium.

If it passes into an optically denser medium, it will slow down.

Question 25

What is refractive index?

Answer 25

A material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material.

Question 26

What is a stationary wave?

Answer 26

A wave that stores, but does not transfer, energy.

Question 27

What is superposition in wave theory?

Answer 27

When two waves meet at the same point in space, their displacements combine and the total displacement becomes the sum of the individual displacements.

Question 28

What is total internal reflection?

Answer 28

An effect that occurs in optical fibres, where full reflection occurs at the inside boundary of the fibre, meaning no radiation passes out. The angle of incidence must be greater than the critical angle for this to occur.

Question 29

What are transverse waves?

Answer 29

A wave with oscillations that are perpendicular to the direction of energy propagation. ## Footnote Electromagnetic waves are examples of transverse waves.

Question 30

What is wave speed?

Answer 30

The product of a wave's frequency and wavelength.

Question 31

What is wavelength?

Answer 31

The distance between two identical positions on two adjacent waves, commonly measured from peak to peak or trough to trough.

Question 32

What is the Young double-slit experiment?

Answer 32

An experiment that demonstrates the diffraction of light by passing monochromatic light across two narrow slits and observing the resulting pattern of bright and dark fringes.

Question 33

What is the equation for wave speed?

Answer 33

Wave speed = frequency x wavelength v = f y (lamda)

Question 34

What is the equation for frequency?

Answer 34

Frequency = 1/ time period f = 1/ T

Question 35

What is the equation for intensity of the wave?

Answer 35

Intensity = power / area over which the wave spreads I = P/A

Question 36

What is the equation for wavelength? (With slits)

Answer 36

Wavelength = slit spacing x distance between fringes on screen / distance from slit to screen

Question 37

What is the equation for Snells law?

Answer 37

Refractive index of the medium A x sin(A) = Refractive index of the medium B x sin(B)

Question 38

What is the equation for angle of refraction when light passes from one medium to another?

Answer 38

Refractive index of first medium x sin(A) = refractive index of second medium x sin(B) N(1) x sin(A) = N(2) x sin(B)

Question 39

What is the equation to find the critical angle at which total internal reflection occurs?

Answer 39

Sin(critical angle) = 1 / refractive index of the denser medium Sin(c) = 1/ n

Question 40

What is the equation for refractive index?

Answer 40

Refractive index = speed of light / speed of light in medium n = c / v

Question 41

What is the wavelength (m) of radio waves?

Answer 41

10^3

Question 42

What is the wavelength (m) of mircowaves?

Answer 42

10^-2

Question 43

What is the wavelength (m) of infrared waves?

Answer 43

10^-5

Question 44

What is the wavelength (m) of visible waves?

Answer 44

10^-6

Question 45

What is the wavelength (m) of ultraviolet waves?

Answer 45

10^-8

Question 46

What is the wavelength (m) of xrays?

Answer 46

10^-10

Question 47

What is the wavelength (m) of gamma rays?

Answer 47

10^-12

Question 48

What is the wavelength (m) of radio waves?

Answer 48

10^3

Question 49

What is the wavelength (m) of mircowaves?

Answer 49

10^-2

Question 50

What is the wavelength (m) of inrared waves?

Answer 50

10^-5

Question 51

What is the wavelength (m) of visible wabes?

Answer 51

10^-6

Question 52

What is the wavelength (m) of ultraviolet waves?

Answer 52

10^-8

Question 53

What is the wavelength (m) of xrasy?

Answer 53

10^-10

Question 54

What is the wavelength (m) of gamma rays?

Answer 54

10^-12

Question 55

How are stationary waves formed?

Answer 55

Stationary waves are formed when two progressive waves with the same frequency and ideally the same amplitude, travelling in the opposite direction superpose.