Waves Flashcards
To revise waves (paper 2)
What do waves transfer?
Energy
What are the two types of wave?
Transverse and longitudinal
Describe a transverse wave
The vibrations of the wave are perpendicular to the direction in which energy is transferred.
Give some examples of transverse waves
Ripples on a water surface
Any wave in the electromagnetic spectrum
Describe a longitudinal wave
The vibrations of the wave are parallel to the direction in which energy is transferred. Longitudinal waves show areas of compression and rarefaction.
Give some examples of longitudinal waves
Sound waves
Ultrasound
Define amplitude
The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position. It shows us how much energy a wave has.
Define wavelength
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave. Measured in meters
Define frequency
It is the number of waves that pass a point per second. Measured in hertz (Hz)
Define period (T)
Its the time for one exact wave to pass a point. Measured in seconds
State the wave equation with all units
wave speed (m/s) = frequency (Hz)× wavelength (m)
Describe an experiment to find the speed of sound through air
Measure a distance of 100 m from a wall. Hit two blocks together to make a sound and start timing. Stop timing when the hear the reflected sound (echo). Divide the time recored by 2. use the equation Speed = distance / time
Describe a method to measure the speed of ripples on a water surface.
Set up a ripple tank. Find the wavelength by using a ruler to measure across 10 wavelengths. Divide the answer by 10 to find 1 wavelength. Use a stopwatch and count the number of waves produced in 10 seconds. Dived the answer by 10 to find the frequency. Use the equation speed = wavelength x frequency
What can happen to waves when they reach a boundary between two materials?
They can be reflected
They can be absorbed (this will cause a small temperature rise)
They can be transmitted (they will pass through)
What is the law of reflection
The angle of incident = angle of reflection for a flat plain mirror.
What is refraction?
When a wave travels from one medium to another and changes direction.
Why does refraction take place?
The change in medium means a change in density which caused a change in speed.
When a substance moves from a more dense to a less dense substance, what is the affect of waves speeds, frequency and wavelength?
Wave speed - decreases
Frequency - same
Wavelength - decreases
When a substance moves from a less dense to a more dense substance, what is the affect of waves speeds, frequency and wavelength?
Wave speed - increases
Frequency - same
Wavelength - increases
State the waves that make up the electromagnetic spectrum, in order of increasing wavelength
Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays
What do all electromagnetic waves have in common?
They are all transverse waves
They can all travel through a vacuum
They all travel at the speed of light through a vacuum
How are radio waves produced?
By an oscillating electrical current.
What happens when radio waves are absorbed by an aerial?
When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself
What are the dangers of ultraviolet waves
Can age skin prematurely
Can burn skin which can lead to skin cancer
Damage eyes which can lead to blindness
What are the dangers of X-rays and gamma rays?
X-rays and gamma rays are ionising radiation
Low doses can damage DNA and cause cancer
Large doses can kill cells
State some uses of radio waves
television and radio, these waves stay within the earths atmosphere.
State some uses of microwaves
Satellite communications eg mobile phone and satellite TV. Microwaves can travel to space and back.
Cooking food.
State some uses of infrared
electrical heaters, cooking food, infrared cameras
State some uses of visible light
fibre optic communications
State some uses of ultraviolet
energy efficient lamps, sun tanning
State some uses of X-rays and Gamma rays
medical imaging and treatments.
