Additional wave properties for separate science Flashcards
Explain how echolocation can be used to measure distances.
To use echolcation you send out a sound wave of known speed. This reflects off an object and is picked up by a detector. The time that it took to go there and back is recoreded.
The distance that the wave travelled when going there and back can be calculated using the formula:
distance = speed x time.
As this is the distance to go there and back, it then needs to be halved to find the distance to the object.
What is the typical range of human hearing?
What happens to the range of audible frequencies as you get older?
the typical range of hearing for a human is 20 Hz to 20,000 Hz
As you get older, this range gets smaller and you loose the ability to hear the highest and lowest frequency sounds
Explain how to use an oscilloscope to measure the frequency of a sound wave
Example: This oscilloscope has been set to a time base (x axis scale) of 5 ms for every large square. what is the frequency of the sound
An oscilloscope shows the wave as a graph of displacment against time. The period of the wave can be found by measuring the number of seconds from one peak to the next.
You can then use the equation:
frequency = 1/period
to find the frequency of the sound wave.
Example: the distance from one peak to the next is 4 squares, which is 20ms. 20ms is 0.02s.
This means that the period is 1/0.02 = 50Hz
Explain how a sound wave is detected by the ear
- The sound waves travels down the ear canal until it hits the eardrum (tympanic membrane)
- The sound wave makes the eardrum vibrate
- the vibrations of the eardrum are passed to the choclear by the three middle ear bones, maleus, incus and stapes
- The sound wave is detected by cillia (hairs) on cells in the cochlear. Depending on which sound waves are formed, difference cells will be stimulated by the wave. Our brain then interprets this information as a sound wave.
compare the motion of sounds through solids and gasses.
Sound waves travel faster in solids than they do in gasses. This is becuase the particles in the medium are closer together, so can pass on the energy more quickly.
Although they travel more quickly the pitch of the sound does not change, this is becuase in a solid the increase in speed is caused by an increase in the wavelength, not the frequency
What is the frequency of ultrasound waves?
Above 20,000 Hz
Where is ultrasonic distance mesurement commonly used?
It is used by animals such as dolphins and bats for echolocation. This is used of locating prey and for navigation.
It can be used medically to scan the unborn fetus. This is done to check for problems with pregnancy and to check the sex of the baby. They are non-ionising so will not affect the health of the fetus
Explain how a medical ultrasound probe works
Medical ultrasound probes can detect multiple depths with one wave due to partial reflection. When the ultrasound wave hits a boundary (change of medium) some of the waves are relected back and others carry on through the body to the next boundary.
By looking at the different times it took for the partially reflected parts of the wave to return, you can calculate how far away from the probe that boundary is. Computers can reconstruct this information into an image.
Explain how you can use an ultrasound probe to calculate the position of a flaw in a metal block
example: the trace on the left shows a normal metal and the trace on the right shows the metal with a spke from a defect (labelled D). if each large square is 1ms, how far away is the defect.
The trace will tell you the time it took for the wave to get to the defect and back again. you can use this equation to calculate the distance away:
distance = 1/2 x speed of sound (m/s) x time taken (s)
Example calculation: The defect took 2ms (0.002 s) to travel there and back. The speed of sound is 330 m/s. Therefore the distance is 330 x 0.002 = 0.66m
Explain how to determine the thickness of a metal block using ultrasound
- Set up the equipment as shown in the diagram
- get the probe to emit a pulse and see how long it takes to be reflected off the back wall.
- use the equation distance = 1/2 x speed x time taken to calculate the distance from the front of the metal blaock to the back
What is the difference between a A-type and a B-type ultrasound scan
An A type scan sends a linear wave of ultrasound towards a target and back
A B-type scan uses a line of ultrasound transduces to detect information from multiple places at once. This creates the fan shaped image that is seen when scanning a fetus.
What are the layers of the earth and the state of matter of each one
inner core - solid
outer core - liquid
mantle - semi-solid
Crust - solid
What are the three types of seismic wave?
What are their relative speeds?
The primary wave (p wave) is a longitudinal wave. It is the fastest wave, which is why it is the first of the waves to be felt.
The secondary wave (S wave) is a transverse wave. It is the second fastest wave and causes the ground to move from side to side. It is the most destructive wave to a building
Long waves are the slowest type of seismic wave. They can only travel through the crust and has a motion which is both forwards and backwards and up and down.
