Topic 4 - Waves Flashcards
Waves
Transfer energy and information in the direction they travel without transferring matter
Frequency
Number of complete cycles of the wave passing a certain point per second
Wavelength
The lenth of a full cycle of the wave(crest to crest or trough to trough)
Amplitude
The displacement from the rest position to a crest a trough
Period
The number of seconds it takes for one full cycle.
Period=
1/Frequency
Wavespeed
The speed at which the wave travels
Wave speed(m/s) =
Distance/Time
What is the wave equation
Wave speed(m/s) = Frequency(hz) x Wavelength(m)
Longitudinal waves
Where the vibrations are parallel to the direction of the wave. Have compressions and rarefactions.
Transverse waves
The vibrations are perpendicular to the direction of the wave
Sound waves are
Longitudinal
P-waves are
Longitudinal
EM waves are
Transverse
Seismic waves are
Transverse
Water waves are
Transverse
Speed of sound waves practical
Use a signal generator to produce sounds with a specific frequency. Attach two microphones to an oscilloscope to find the wavelength of the sound waves. Then use v = fλ.
Speed of water ripples practical.
Use a signal generator attached to the dipper of a ripple tank to create certain frequency waves. Turn on the strobe light and alter its frequency until the wave pattern on the screen stops moving. Measure the distance between lines that are 10 wavelengths apart and find the average wavelength. Then use v = fλ
Wave absorbtion effect
The wave transfers energy to the materials energy stores. Often it is transferred to the thermal energy store which leads to heating.
Wave transmission effect
The wave carries on travelling through the new material. Often leads to refraction.
Wave reflection effect
The wave is sent back away from the material. How echoes are created.
Wave refraction effect
When a wave is transmitted through a boundary and changes direction.
How does refraction occur
When a wave crosses a boundary into a different density material, it changes speed. This leads to change in direction.
Which way does a wave refract
If a wave is travelling along the normal it will change speed but not change direction. If it slows down it bends towards the normal, and if it speeds up it travels away from the normal
What determines if a wave get reflected, absorbed etc…
Depends on the wavelength of the wave and the properties of the material
How are sound waves produced
Vibrating objects are passed through the surrounding medium as a series of compressions and rarefactions.
Eardrum
Sound waves cause it to vibrate
Ossicles
Tiny bones in the ear that recieve the vibrations from the ear drum
Semicircular canals
From the ossicles to the cochlea
Cochlea
Turns vibrations into electrical signals
Auditory nerve
Carries elctrical signals to the brain
Ultrasound
Sound waves with frequency of more than 20,000Hz
Infrasound
Sound waves with frequency of less than 20,000Hz
Sonar
Used by boats and submarines to send ultrasound to the surface and measure distance of objects underwater.
Foetal scanning
Ultrasound is sent int othe womb to produce a video image of the foetus.
Explorations of the earths core
Seismic waves(P and S-waves) act differently so are used to explore the size and properties of the earths inside.
How do velocity, frequency and wavelength change and link in sound waves travelling between mediums
When a sound waves is transmitted througha boundary from one medium to another, velocity changes. Frequency doesnt change meaning that wavelength must change. When velocity increases, so does wavelength and vice versa.
