National 5 Waves Flashcards
Factual Recall
1.1 What does a wave transfer?
A wave transfers Energy
1.2 Explain the difference between a transverse and longitudinal wave.
In a transverse wave the medium oscillates at right angles to the direction of energy transfer.
In a longitudinal wave the medium oscillates parallel to the direction of energy transfer.
1.3 Classify examples of transverse and longitudinal waves.
Longitudinal: Sound
Transverse: Water, Light, Radio Waves, All Electromagnetic Waves
1.4 Define Frequency
Frequency (f) is the number of waves per second.
It is measured in Hertz (Hz).
1.4 Define Wavelength
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.
1.4 Define Period
Period (T) is the time for one complete wave.
It is measured in seconds (s).
1.4 Define Amplitude
Amplitude (A) is the height of a wave from the middle (line of zero disturbance) to the top (crest), or from the bottom (trough) to the middle.
It is measured in metres (m).
For example, D in the attached image.
1.4 Define Speed
Speed (v) is the distance travelled per unit of time by a wave.
It is measured in metres per second (ms-1).
1.4 Define a Crest
A Crest is the highest point of a wave.
For example, B in the attached image.
1.4 Define a Trough
A Trough is the lowest point of a wave.
For example, C in the attached image.
1.5 f = 1/T
(Define symbols and units)
f - frequency (Hz)
T - period (s)
1.5 Example
A bat emits ultrasounds with a period of 23 µs. Calculate the frequency of the ultrasound.
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
1.5 f = N/t
(Define symbols and units)
f - frequency (Hz)
N - Number of waves (no units)
t - time (s)
1.5 Example
A siren produces 26,400 waves per minute.
Calculate their frequency.
N = 26,400 t = 1 min = 60 s f = ?
f = N/t f = 26,400/60 f = 440 Hz
1.6 v = f λ
(Define symbols and units)
v - speed (ms-1)
f - frequency (Hz)
λ - wavelength (m)
1.6 Example
Some water waves have a wavelength of 2 m and a frequency of 6 Hz.
Calculate their speed.
v = ? f = 6 Hz λ = 2 m
v = fλ v = 6 x 2 v = 12 ms<sup>-1</sup>
1.6 d = vt
(Define symbols and units)
d - distance (m)
v - speed (ms-1)
t - time (s)