Waves Flashcards
State the two types of waves
Transverse and logitudinal
Describe a transverse wave
A wave with oscillations at right angles/perpendicular to the direction of energy transfer
Describe a longitudinal wave
A wave with oscillations parallel to the direction of energy transfer
Give two examples of transverse waves
EM waves including light, water waves
Give one example of a longitudinal wave
Sound
Define amplitude
The vertical distance from the middle point to the peak/crest or the trough
Define wavelength
The horizontal distance from the peak/crest of one wabe to the peak/creast of the next wave (one full wave)
Define displacement
The distance from the lowest point of a wave (trough) to the highest point of a wave (peak/crest)
What is a wave’s period?
The time it takes to complete one full wave
What is the equation which links wave speed, wavelength and frequency?
V = f x λ
Define frequency
How many waves there are per second
What are the units for frequency?
Hertz (Hz)
State the seven EM waves in order of increasing frequency
Radio waves, micro waves, infrared, visible light, ultra violet, x-rays, gamma rays
State the uses of radio waves
TV signals, satellite communications
State the uses of micro waves
Cooking food, mobile phone signals
State the uses of infrared radiation
Thermal imaging cameras/night vision cameras, cooking and heating
State the uses of visible light
Photography
State the uses of ultra violet
Tanning beds, detecting forged bank notes (invisible secruity markings), sterilising water
State the uses of x-rays
Airport scanners, detecting broken bones
State the uses of gamma rays
Treating cancer, sterilising food and medical equipment
What is ionising radiation?
Radiation that turns atoms into ions
What are the dangers of ionising radiation?
Damage to DNA and cells, mutations, uncontrolled cell growth/tumours, cancer
If wave speed is constant, how are frequency and wavelength linked?
They are indirectly propertional - as one increases, the other decreases
At what speed do all EM waves travel in a vacuum?
3 x 108 m/s
How do you measure wavelength using a ripple tank?
Use a strobe light to form a still image of the waves, measure the length of 10 waves and divide by 10 to get the wavelength of one wave
How do you measure frequency using a ripple tank?
Count the number of waves passing a certain point in 30 seconds and divide by 30 to get the number of waves per second
How do you calculate wave speed in a ripple tank without wavelength and frequency?
Measure the length of the ripple tank, time how long it takes for one wave to travel from one end to the other and use the equation: v = s/t
How do you measure wavelength using waves on a string?
Measure the length of the string and divide it by the number of half waves to get half a wavelength. Multiply by two to get one full wavelength
How do you generate a wave on a suspended string?
Using a signal generator with a set frequency
Describe diffuse reflection
When light hits a rough surface, the light rays bounce off in different directions
Describe specular reflection
When light hits a smooth surface, the light rays bounce off in the same direction to form a mirror image
What is the law of reflection?
The angle of incidence is equal to the angle of reflection
Describe refraction from air into water or glass
When a wave passes from a less dense medium into a more dense medium, the wave slows down and changes direction
Describe refraction from water or glass into air
When a wave passes from a more dense medium into a less dense medium, the wave speeds up and changes direction
What is the normal?
A perpendicular line at right angles to a surface
On a wave front diagram, how could we show that a wave has slowed down?
The wave fronts would be closer together
On a wave front diagram, how could we show that a wave speeds up?
The wave fronts would be further apart
Describe diffraction
The bending of a wave around objects or through gaps between objects
How will a narrow gap affect a wave?
The wave will curve more
How will a wide gap affect a wave?
The wave will curve slightly at the edges
Which surfaces are the best absorbers and emitters of infrared radiation?
Black, matt surfaces
Which surfaces are the worst absorbers and emitters of infrared radiation?
Light, shiny surfaces
Which surfaces are the best reflectors of infrared radiation?
Light, shiny surfaces
Which surfaces are the worst reflectors of infrared radiation?
Black, matt surfaces
What is the relationship between wave speed, wave frequency and wavelength ?
wave speed = frequency × wavelength
What happens to light as it travels from a less dense to a more dense medium?
Slows down and bends towards the normal
