National 5 Waves Flashcards

Factual Recall

You may prefer our related Brainscape-certified flashcards:
1
Q

What do all waves wave transfer?

A

All wave transfer Energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain the difference between a transverse and longitudinal wave.

A

In a transverse wave the particles of the medium oscillate at right angles to the direction of energy transfer.

In a longitudinal wave the particles of the medium medium oscillate parallel to the direction of energy transfer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give and example of a longitudinal and a transverse and a wave.

A

Longitudinal: Sound

Transverse: Water, Light, Radio Waves, All Electromagnetic Waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define Frequency

A

Frequency (f) is the number of waves produced (or passing a point) per second.

It is measured in Hertz (Hz).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

1.4 Define Wavelength

A

Wavelength (greek letter lambda λ) is the length of one complete wave, often measured between successive crests or troughs.

It is measured in metres (m).

For example, A in the image.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define the Period of a wave.

A

The Period (T) of a wave is the time taken to produce for one whole wave.
(One whole crest and one whole trough).

It is measured in seconds (s).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define the Amplitude of a wave.

A

Amplitude is the height of a wave from the line of zero disturbance to the top of a crest, or from the line of zero disturbance to the bottom of a trough.

It is measured in metres (m).

For example, D in the attached image.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define the Speed (v) of a wave.

A

The Speed (v) is the distance travelled per unit of time by a wavefront.

It is measured in metres per second (ms-1).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define a Crest

A

A Crest is the highest point of a wave.

For example, B in the attached image.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define a Trough

A

A Trough is the lowest point of a wave.

For example, C in the attached image.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which feature of a wave is measure of its energy?

A Wavelength
B Frequency
C Speed
D Amplitude
E Period

A

D Amplitude

The greater the amplitude of a wave, the greater its energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

f = 1/T

(Define symbols and units)

A

f - frequency (Hz)

T - period (s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Example

A bat emits ultrasounds with a period of 23 µs. Calculate the frequency of the ultrasound.

A
T = 23 µs = 23 x 10<sup>-6</sup> s
f = ?
f = 1/T
f = 1/23 x 10<sup>-6</sup>
f = 4.35 x 10<sup>4</sup> Hz
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

f = N/t

(Define symbols and units)

A

f - frequency (Hz)

N - Number of waves (no units)

t - time (s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Example

A siren produces 26,400 waves per minute.

Calculate their frequency.

A
N = 26,400
t = 1 min = 60 s
f = ?
f = N/t
f = 26,400/60
f = 440 Hz
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

v = f λ

(Define symbols and units)

A

v - speed (ms-1)

f - frequency (Hz)

λ - wavelength (m)

17
Q

Example

Some water waves have a wavelength of 2 m and a frequency of 6 Hz.

Calculate their speed.

A
v = ?
f = 6 Hz
λ = 2 m
v = fλ
v = 6 x 2
v = 12 ms<sup>-1</sup>
18
Q

d = vt

(Define symbols and units)

A

d - distance (m)

v - speed (ms-1)

t - time (s)

19
Q

Example

A cannon is 170 m away.

The sound from the cannon firing takes 0.5 s to reach you.

Use this to calculate a value for the speed of sound in air.

A
v = ?
t = 0.5 s
d = 170 m

d = vt
170 = v x 0.5
v x 0.5 = 170
v = 170/0.7
v = 340 ms-1

20
Q

Example

An ultrasound scanner detects an echo from a baby’s head after 0.12 ms.

How far away is the baby’s head?

(Take the speed of sound in tissue to be 1500 ms-1

A

Don’t forget that in an echo problem the echo has to travel there and back.

v = 1,500 ms<sup>-1</sup>
t = ½ x 0.12 ms = ½ x 0.12 x 10<sup>-3</sup> = 6 x 10<sup>-5</sup> s (half for there only)
d = ?

d = vt
d = 1,500 x 6 x 10-5
d = 0.09 m
The baby’s head is 0.09 m away.

21
Q

What is meant by diffraction?

A

Diffraction is when a wave bends round an obstacle or through a gap.

22
Q

What are the practical limitations of diffraction?

A

If an object is small compared to the wavelength, the wave will bend round the object and it cannot be detected.

If a gap is small compared to the wavelength, significant diffraction occurs leading to semicircular wavefronts.

23
Q

State the effect of wavelength on diffraction.

A

Longer wavelengths diffract more than shorter wavelengths.

24
Q

What is meant by the electromagnetic spectrum?

A

The electromagnetic spectrum is a family of waves which all travel at the speed of light and can travel through a vacuum (no medium required).

They all have different wavelengths and frequencies. All are invisible except visible light.

25
Q

List the members of the electromagnetic spectrum in order of increasing wavelength.

A

Gamma, X-Rays, Ultraviolet, Visible, Infrared, Microwaves, Radio Waves

26
Q

Give one typical source, detector and application for Gamma Rays

A

Source: Nuclear Decay, Cosmic Rays, Stars

Detector: Geiger-Muller Tube, Photographic Film

Applications: Treating Cancer (Radiotherapy), Tracers to diagnose illness

27
Q

Give one typical source, detector and application for X-Rays

A

Source: Man-made electronic sources, Stars

Detector: Photographic Film, Transistor arrays.

Applications: Diagnosing broken bones

28
Q

Give one typical source, detector and application for Ultraviolet

A

Source: Ultra-Hot objects, Electrical discharges/sparks, Stars

Detector: Diode-probe receiver, Photographic Film, Chemical Flourescence

Applications: Dental Curing (Setting fillings in teeth), Tanning Beds (don’t use them kids!).

29
Q

Give one typical source, detector and application for Visible Light

A

Source: Very-Hot objects (lamps), Electrical discharges/sparks, Stars

Detector: Photographic Film, Photodiode, Charge-Coupled Device (CCD), Human Retina

Applications: Seeing

30
Q

Give one typical source, detector and application for Infrared

A

Source: Hot objects, Stars

Detector: Thermometer, Photodiode, thermochromic film.

Applications: Optical fibre communication, Remote controls, “Night” vision

31
Q

Give one typical source, detector and application for Microwaves

A

Source: Electrical circuits, Stars

Detector: Diode Probe Receiver

Applications: Telephone Communications, Cooking.

32
Q

Give one typical source, detector and application for Radio Waves

A

Source: Electrical circuits, Stars

Detector: Aerial

Applications: Mobile Phone signals, Television signals

33
Q

Comment on the speed of Electromagnetic Waves

A

All Electromagnetic Waves travel at the same speed, which is the speed of light (3 x 108 ms-1).

34
Q

Example

Microwaves have a frequency of 9.4 GHz. Calculate their wavelength.

A
v = 3 x 10<sup>8</sup> ms<sup>-1</sup> (Since EM Wave)
f = 9.4 GHz = 9.4 x 10<sup>9</sup> Hz
λ = ?

v = fλ
3 x 108 = 9.4 x 109 x λ
9.4 x 109 x λ = 3 x 108
λ = 3 x 108/9.4 x 109
λ = 0.032 m

35
Q

Example

Radio Waves takes 1.28 seconds to travel from the moon to the earth. How far away is the moon?

A
v = 3 x 10<sup>8</sup> ms<sup>-1</sup> (since EM Wave)
t = 1.28 s
d = ?

d = vt
= 3 x 108 x 1.28
d = 3.84 x 108 m

36
Q

Example

The sun is 1.5 x 1011 m away.

How long does it take light to travel from the sun to the Earth?

A
v = 3 x 10<sup>8</sup> ms<sup>-1</sup> (since EM Wave)
d = 1.5 x 10<sup>11</sup> m
t = ?

d = vt
1.5 x 1011 = 3 x 108 x t
3 x 108 x t = 1.5 x 1011
t = 1.5 x 1011/3 x 108
t = 500 s

37
Q

Define Refraction

A

Refraction is the change in speed (or wavelength) that occurs when a wave travels from one medium to another.

Note - the direction need NOT change upon refraction and need not be mentioned in its definition.

38
Q

Identify correctly the angle of incidence, angle of refraction and normal in ray diagrams showing refraction.

A

The normal is an imaginary line at right angle to the surface where a ray strikes. (The dashed grey vertical line in the image)

The angle of incidence is the angle between the incident ray and the normal. (P in the image)

The angle of refraction is the angle between the refracted ray and the normal. (Q in the image)

Remember
In optics, we always measure angles between the ray and the normal.