Paper 2 - 6 Waves Flashcards
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. Infrasound. P-waves.
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) x 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 sound wave moves from a more dense to a less dense substance, what is the effect on wave speed, frequency and wavelength?
Wave speed - decreases Frequency - same Wavelength - decreases
When a sound wave moves from a less dense to a more dense substance, what is the effect on wave speed, frequency and wavelength?
Wave speed - increases Frequency - same Wavelength - increases
State the normal human hearing range
From 20 Hz to 20 kHz
How do we detect sound waves?
Within the ear, sound waves cause the ear drum and other parts to vibrate. These vibrations are converting into an electrical signal which is passed onto the brain.
Why do humans have a limited range of frequencies they can detect?
The conversion of sound waves to vibrations of solids works over a limited frequency range. This restricts the limits of human hearing.
What is the effect of a louder sound on the ear drum?
Larger vibrations
What is the effect of a higher pitched sound on the ear drum?
Faster vibrations
What is a ultrasound?
Ultrasound waves have a frequency higher than the upper limit of hearing for humans (20000 Hz)
How can ultrasound be used for medical and industrial imaging?
Ultrasound waves are partially reflected and partially transmitted when they meet a boundary between two different media. The time taken for the reflections to return to the detector can be used to determine how far away such a boundary is.Distance = speed x time
What are seismic waves
Waves produced by Earthquakes