P5.1 + 2 - Waves Flashcards
Longitudinal waves
Series of rarefactions and contractions that go parallel to propagation that transfer particles
Transverse waves
Travel at a right angle to propagation and do not transfer particles
Amplitude
Distance from top to middle of a wave
Wavelength
Distance from one point of wave to the next identical
Frequency
No. of waves per second 1/T
Time period
Time for one wave to pass in given time 1/F
Wave velocity equation
Velocity (m/s) = wavelength (m) * frequency (Hz)
Velocity of ripples
- find wavelength using strobe band ruler
- fine frequency by no. of rotations per second of motor
- apply equation
Velocity of wave changes
When travelling through different mediums called refractions
Travelling through solids
Increases velocity because more particles are able to vibrate
What can happen to sound
- reflected
-transmitted (refracted)
-absorbed
ultrasound frequency
20KHz
How does ultrasound work
- transmitter beams ultra waves
-waves reflect at different boundaries - machine calculates distance from SDT to produce image
Ear detect sound
- waves travel through auditory canal to ear drum
-drum vibrates and passes to ossicles (hammer anvil and stirrup) - act as lever to amplify vibrations
- through into cochlea where hairs vibrate
-vibrations to auditory nerve where brain converts to sound
Short hairs in cochlea
Vibrate at high frequencies
Long hairs in cochlea
Vibrate at small frequency
As you get older…
You lose cochlea hair (short ones) which makes it harder to hear high frequency
EM spectrum
-radio
-micro
-infrared
- visible
-uv
-xrays
-gamma
Which em wave has highest wavelength
Radio
Which em has largest frequency
Gamma
Em velocity
3.0 * 10^8 m/s
How to produce radio waves?
-oscillating pd across wire makes electrons move forward and back
-Produces changing elec and mag field as radio wave
-when connected creates em wave by moving electrons
Uses of waves
Radio - radio stations
Microwave - Wi-Fi and ovens
Infrared - cooking food
Visible - light or torches
UV - produce vitamin and kill bacteria
X-rays - kill skin cancer
Gamma - kill cancer and bacteria
Danger of em
UV - damage skin cells by growing very rapidly
X-rays - cause skin cancer
Gamma - kill cells in body
