Waves (wave properties - waves for detection and exploration) Flashcards
What is the equation for period
1/frequency
what is the equation for wave speed?
frequency x wavelength
What are transverse waves?
waves that oscillate perpendicular to the direction of energy transfer
what are the longitudinal waves?
waves that oscillate parallel to the direction of energy transfer
What is the definition of frequency?
the number of waves passing a fixed point per second
what is amplitude?
the maximum displacement that any particle achieve from its undisturbed position
what is the wavelength?
the distance from one point on a wave to the equivalent point on the next wave
what is a period?
the time taken for one complete oscillation in seconds
What do waves transfer?
energy
NOT MATTER
what is the relationship between the wavelength and speed?
they are directly proportional
What happens when a wave is transmitted from one medium to another
their speed and wavelength changes
frequency stays the same
Why does the frequency stay the same when a wave is transmitted from one medium to another?
because the same number of waves is still being produced by the source per second
What does the amplitude indicate?
the amount of energy a wave is carrying
the more energy the higher the amplitude
When waves reach a boundary between one medium and another, they can be …….
reflected, refracted, absorbed or transmitted
What does the direction of refraction depend on?
- the angle at which the wave hits the boundary
- the materials involved
what happens when light travels from a material with a low refractive index to one with a higher refractive index?
it bends towards the normal
- slows down
high refractive index to low refractive index =
bends away from the normal
- speeds up
Refraction is due to ……
difference in the wave speed in the different media
What happens when light enters, at an angle, a medium in which it travels slower
- the first part of the light wave to enter the medium slows down
- the rest of the wave continues at the higher speed
- causes the wave to change direction towards the normal
what does the amplitude in sound indicate?
its volume
high = loud
what does the frequency in sound indicate?
pitch
high frequency = high pitch
What is the normal range of human hearing
20hz - 20,000 hz
sound is due to …..
the vibration of particles that make up matter
sound cant travel in _________
a vacuum
Within the ear sound waves causes…
the ear drum and other structures to vibrate- vibration heard as sound
what frequency does ultrasound have?
higher than 20,000 hz
What happends when ultrasound waves are directed into an object and arrive at a boundry between one material and another?
they will be partially transmitted and partially reflected
How do you determine how far way a boundry is?
by measuring the time taken for reflected ultrasonic waves to return to a detector
How can ultrasound be used for medical imaging?
1) ultrasound waves pass through the body but when they reach the boundry between two different media ( like fluid in the womb and the kin of the foetus) some of the wave is reflected back and detected
2) the exact timing and distribution of these echoes are processed by the computer to produce a video image of the foetus
An example of how ultrasound can be used for industrial imaging
finding flaws in material
what is echo sounding (sonar)
the use of ultrasonic waves for detecting objects in deep water and measuring the depth of water
Features of P-waves
- logitunidal
- travel at the speed of sound
- twice as fast as s-waves
- travel at different speeds through solids and liquids
Features of S-waves
- transverse
- can’t travel through liquids
why do seismic waves travel in a curved path through the Earth?
Due to the Earth increasing with density with depth
and when they are refracted they change their speed gradually
S- wave shadow zone is due to…
s-waves not being able to travel through the liquid outer core of the earth; provides evidence of the size of the Eath’s core
What happens when seismic waves reach a boundary between different layers of material?
some are absorbed, some are refracted
P waves shadow zone is due to:
- waves being refracted at the boundary between the semi-solid mantle and the liquid outer core
- waves are refracted again at the boundary between the liquid outer core and solid inner core
what are the p- waves shadow zone used to determine?
the size and composition of inner and outer core
total internal reflection can only happen when…
the light ray is going from a dense to a less dense medium
What happens when the angle of incidence is less than the critical angle?
Most of the light passes (refracted) out but a little bit is internally reflected
What happens when the angle of incidence is equal to the critical angle?
the angle of refraction is 90 degrees
What happens when the angle of incidence is greater than the critical angle?
no light is refracted and all of the light is internally refracted creating total internal reflection
What is compression and rarefraction?
compression = compressed region of longitudinal waves
rarefaction = stretched region of longitudinal waves
What is the Doppler effect?
What happens when the source moves towards the observer and away from the observer
What increases the Doppler effect?
The apparent difference between the frequency at which sound or light waves leave a source and that at which they reach an observer, caused by relative motion of the observer and the wave source.
- towards = frequency increases and wavelength decreases
- away = frequency decreases and the wavelength increases
the faster the movement, the greater the doppler shift
