P3.3 Flashcards
What do waves transfer ?
Energy
What are the two types of waves ?
Longitudinal, Transverse
What are longitudinal waves ?
Longitudinal waves have oscillations which are parallel to the direction of energy transfer
What are the squished and stretched parts of a longitudinal wave called ?
Compression, rarefaction
Give an example of a longitudinal wave.
Sound wave
What is a transverse waves ?
Transverse waves have oscillations that are perpendicular to the direction of energy transfer
Give an example of a Transverse wave.
Light, sea wave
What can happen when a wave arrives a boundary between two different materials ?
The wave can be reflected, refracted or absorbed
What is reflection ?
Reflection is when light bounces back the direction it came from at a boundary between materials
What is refraction ?
Refraction is when light changes speed as it moves from one medium to another, so light bends towards or away from the normal
What is the frequency of a wave ?
Frequency is the number of waves that pass a point each second
What is the unit of frequency ?
Hertz (Hz)
What is a period ?
A period is the length of time it takes one wave to pass a given point
What is the unit of a period ?
Seconds (s)
What is the definition of wavelength ?
Wavelength is the distance from one point on one wave to the identical point on the next wave.
What is the unit of wavelength ?
Metres (m)
What is the definition of amplitude ?
The maximum distance of a point on the wave from its rest position
What is the peak of a wave ?
The peak is the highest point of a wave
What is the trough of a wave ?
The trough is the lowest point of a wave
What frequencies can humans hear ?
Humans can only hear frequencies between 20 and 20,000 Hz
What is any sound above 20,000 Hz called ?
An ultrasound
What is the velocity of a wave ?
Speed in the direction the wave is travelling
What is the equation that links velocity of a wave, displacement and time ?
Velocity = displacement/time
What is the equation that links velocity of a wave, frequency and wavelength ?
Velocity = frequency x wavelength
What is the unit of velocity ?
Metres Per second (m/s)
What is the unit of displacement ?
Metres (m)
What is the unit for time ?
Seconds (s)
Can waves travel through solids,causing vibrations ?
Yes
Can sound waves travel through air ?
Yes
Why do people hear sounds ?
As the sound wave vibrates on their eardrum
What are 2 ways we can investigate waves ?
Ripple tank, string and a frequency generator
How can you calculate wave speed ?
Frequency x wavelength
How does ultrasound work ?
Ultrasound waves are partially reflected at the boundary between two materials. The time taken to reach a detector can determine how far away an object is
What can ultrasound be used for ?
Seeing unborn babies, finding cracks in pipes and finding how far away underwater objects are
What are seismic waves
Earthquakes
What can seismic waves help us understand ?
The structure of the earth
What are the two types of seismic waves ?
S waves and P waves
What is a P wave ?
A longitudinal seismic wave
What is a S wave ?
A transverse seismic wave
Can S waves travel through liquid ?
No
Can P waves travel through both solids and liquids ?
Yes, P waves travel at different speeds through solids and liquids
What are the different ways that energy can be transferred ?
Mechanically, heating, electric current, waves
Name the 8 energy stores.
Chemical, elastic potential, magnetic, electrostatic, nuclear, thermal, kinetic, gravitational
What is a way to calculate the frequency of a wave with only the time period ?
Frequency = 1/time period
What does a higher frequency mean on an oscilloscope screen ?
Higher pitch
What does a higher amplitude mean on a oscilloscope screen ?
Louder sound
What is the definition of speed.
Distance travelled per unit time
Is speed a vector or scalar quantity?
Scalar
Is velocity a scalar of vector quantity?
Vector
What is the law of reflection?
The angle of incidence = the angle of reflection
What happens when light moves from a more dense medium to a less dense medium ?
It bends away from the normal
What happens to the wavelength, speed and frequency when a wave enters a new medium ?
The wavelength and speed change but the frequency stays the same
What happens when light moves from a less dense material to a more dense material ?
Part reflects and part refracts
How would you calculate frequency from a ripple tank ?
Count the number of waves passing a fixed point in 20 seconds and then divide by the number of seconds (20)
How would you calculate wavelength from a ripple tank ?
Using the ruler measure the length across as many waves as possible then divide by the number of waves
What is each ripple called in a ripple tank?
A wave front
How are plane (straight) waves produced in a ripple tank ?
By repeatedly dipping the (long edge of a ruler) into the water
What are the waves called (in a ripple tank) as they approach the barrier ?
Incident waves
What are waves called (in a ripple tank) when they reflect off the barrier ?
Reflected waves
How does sound travel through the air ?
Vibrations of a source cause layers of air particles beside it to vibrate this then makes layers of air particles next to them vibrate
What does a transducer do ?
A transducer produces and detects sets (or pulses) of ultrasound waves
What are two advantages to using ultrasound compared to x-rays ?
- ultrasound can be used to scan organs and other soft tissues in the body
- ultrasound is non ionizing and is harmless to use
