P12 - Wave Properties Flashcards
What categories of waves do all waves fall under
Either transverse or longitudinal
Direction of oscillations to energy transfer in transverse waves
The oscillations are perpendicular to the direction of energy transfer
The direction of energy transfer is sideways but the oscillations go up and down
What do longitudinal waves have that transverse waves don’t
- They have compressions (regions with lots of particles) and rarefactions (regions with less particles)
Direction of oscillations to energy transfer in longitudinal waves
The oscillations are parallel to the direction of energy transfer
Do longitudinal or transverse waves need a medium to travel
All logitudinal waves do but not all transverse waves do
What is the amplitude of a wave
The maxium displacement of a point on a wave away from its undisturbed position
What is the wavelength of a wave
The distamce from one point on one wave to the equivalent point on the adjacent wave
It is measured in lambda (λ)
What is the frequency of a wave
The number of waves passing a point each second
It is measured in Hertz (Hz)
What is the period of a wave and its equation
The time it takes for one wave to pass a certain point
period (s) = 1/frequency
(T = 1/f)
What is the wave speed
The spped at which the wave moves through the medium (the speed of energy transfer as waves transfer energy, not matter)
Equation for wave speed
v = fλ
wave speed(m/s) = frequency(Hz) x wavelength(m)
Method to find the speed of sound waves in air
- Seperate 2 people by 500m on a flat area
- Give one a pair of cymbals and the other a stopwatch
- Person A clashes the cymbals together and Person B start the timer when they see this happening
- Person B stops the stopwatch when they hear the cymbal crash
- To find the speed, you divide the distance by the time
Problems with the method to find the speed of sound waves and fixes
- Everyone has a different reaction time - it takes time between seeing the cymbals and starting the timer and then hearing the sound and stopping the timer
- This can be reduced by having lots of people with timers to discount anomalies and find a emean
- The time between seeing and heaaring is very short - this can be reduced by using a larger distance
What 3 things could happen when a wave hits a boundary between two different materials
- It could be transmitted (includes refraction)
- The energy of the wave could be absorbed
- The surface of the material could reflect the wave
What happens to a wave when it travels from one medium to another
- Its speed and wavelength change and they are directly proportional
- But its frequency stays the same because the source is producing the same amount of waves per second
Relationship between the angles of reflection and incidence
they are the same
How does the ear work to help us hear sound
- Sound waves are funneled into the ear canal and hit the ear drum
- The sound waves cause the ear drum to vibrate
- The conversion of sound waves to vibration only happens over a limited frequency however
Range of normal human hearing
20 - 20000Hz
What do the frequency and amplitude of sound waves represent
- Frequency is the pitch. High frequency means high pitched
- Amplitude is the volume. A large amplitude means a loud sound
What is a reflected sound wave called
An echo
What is ultrasound
Sound waves with a frequency higher than the upper limit of human hearing
They partially reflect at the boundary between two densities
Uses of ultrasound
The time taken for an ultrasound relfection can be measured using a detector
This means it can be used in medical and industrial imaging e.g. to see organs or metal defects
What are P waves
Longitudinal waves than can pass through liquids and solids, They aslo travel faster than S waves
What are S waves
Theya re transverse waves that can only travel through solids
How do seismic waves provide evidence of the internal structure of the earth
- S waves can only be detected on certain parts of the crust and there is an S wave shadow zone
- This is because S waves cannot pass through liquids so the Earth must wave a liquid core
- There are also P wave shadown zones and this is due to P waves travelling faster in solids than liquids
- This causes them to refract in the liquid outer core
