Waves Flashcards
What is the function of a progressive wave?
They transfer energy from point A to point B through vibrations
What is a longitudinal wave?
Give an example.
- A wave in which the vibrations are parallel to the direction of the wave/wave propegation
- e.g. sound and ultrasound
What is a transverse wave?
Give an example.
- A wave in which the vibrations are perpendicular (at 90º) to the direction of the wave/wave propegation
- e.g. water waves, electromagnetic waves
What is the definition of frequency?
The number of complete waves passing a point in 1 second
(Measured in Hertz (Hz or 1/s))
What is the definition of wavelength?
The distance between two consecutive crests/peaks or troughs (m)
What is amplitude?
The maximum displacement of the wave from its rest/equilibrium position (m)
What is periodic time?
The time for one complete wave or vibration
(Measured in seconds (s))
What is ultrasound?
The sound of a frequency greater than 20000 Hz
What is echo?
The reflection of a wave by a surface or object so that a weaker version of it is detected shortly after the original
What is radar?
The use of reflected radio waves to track fast-moving objects e.g. aircraft
What is sonar?
The use of ultrasound echoes to measure distances and form images e.g. of a unborn baby or seabed
What is refraction of waves?
The change in direction of a wave due to a change in refraction index
and
its speed changes
(FAST: Faster Away; Slower Towards)
What are electromagnetic waves
transverse waves which travel at the speed of light (3 x 108m/s) in a vacuum.
In increasing wavelength: Gamma rays; x-rays; ultra-violet; visible; infra-red; microwaves; radio waves
What happens when circular waves are reflected from a straight barrier?
The waves move with the same wavelength and speed of the wave they are reflecting
The centre point of reflected waves are the same distance from the barrier as the centre point of incident waves
How are waves reflected by a parallel barrier?
The waves remain straight and keep the same wavelength and speed as the incident waves
How are straight waves reflected at a 45º angle from a straight barrier? (2)
- Incident angle = reflected angle (angle from normal to wave)
- They also have the same wavelength and speed
How do waves change when travelling from deep to shallow water? (3)
- wavelength decreases
- speed decreases
- Frequency constant
What is the equation relating to wave’s wavelength, frequency and velocity?
Give units
v = fλ
Velocity = frequency x wavelength
Velocity = m/s
Frequency = Hz / S-1
Wavelength = m
V
fλ
How do waves change when travelling from shallow to deep water? (3)
- wavelength increases
- speed increases
- Frequency constant
What is the order of electromagnetic waves in terms of wavelength?
- Radio
- Microwaves
- Infrared
- Visible (light)
- Ultra Violet
- X-ray
- Gamma
1st being largest
What are some common uses of each member of the electromagnetic spectrum?
- Radio - telecommunications
- Microwaves - heating food
- Infrared - heating
- Visible (light) - photography
- Ultra Violet - tanning booths and counterfeit money detection
- X-ray - medical diagnostics
- Gamma - sterilising surgical equipment
What are the two pneumonics for speed of sound waves after refraction?
Fast
Towards normal
Slow
Slow
Away from normal
Fast
What are the two pneumonics for mediums for refraction?
Less dense
Towards normal
More dense
More dense
Away from normal
Less dense
(In relation to the normal)
What are the two forms of waves? What direction do they travel?
- transverse (perpendicular to linear propegation)
- longitudinal (parallel to linear propegation)
What are rarefactions?
Places where the particles in a longitudinal wave are least tightly packed together
What is a mechanical wave?
A wave that requires particles/matter
