Waves

Question 1

What do waves transfer and not transfer?

Answer 1

Transfer: energy
Don’t transfer: matter

Question 2

How are all waves produced? What are the names of the two types?

Answer 2

Through vibrations. They can be classified as TRANSVERSE or LONGITUDINAL.

Question 3

What way do the vibrations OCCUR in a transverse wave?

Answer 3

Perpendicular to the direction in which the wave is travelling.

Question 4

What way do the vibrations OCCUR in a longitudinal wave?

Answer 4

Parallel to the direction in which the wave is travelling.

Question 5

What are the only two longitudinal waves?

Answer 5

Sound and ultrasound.

Question 6

What is the wavelength of a wave? What is it usually measured in?

Answer 6

The distance between two consecutive crests or troughs. It is usually measured in metres, m.

Question 7

What is the frequency of a wave? What is it usually measured in?

Answer 7

The numbers of waves that pass a point in one second. It is usually measured in Hertz, Hz.

Question 8

What is the period of a wave? What is it usually measured in?

Answer 8

The time taken for one complete wave to pass a point. It is usually measured in seconds, s.

Question 9

What is the amplitude of a wave? What is it usually measured in?

Answer 9

The MAXIMUM displacement of a wave from equilibrium position. It is usually measured in metres, m.

Question 10

What is period related to? What is wavelength related to?

Answer 10

Period: time
Wavelength: distance

Question 11

When the turns of a coil are close together what is it called?

Answer 11

A compression.

Question 12

When the turns of a coil farthest apart what is the called?

Answer 12

A rarefaction.

Question 13

In terms of compressions and rarefactions, how do you find the wavelength of a longitudinal wave?

Answer 13

The distance between the centres of two consecutive compressions or rarefactions.

Question 14

What is the wave equation? What is each component measured in?

Answer 14

Wave speed (v) = frequency (f) x wavelength (lambda)
Metres/second, m/s = Hertz, Hz x metre, m

Question 15

What is the range of human hearing?

Answer 15

From 20 Hz to 20,000 Hz.

Question 16

Sound at frequencies above 20 KHz cannot be heard and is called what?

Answer 16

Ultrasound.

Question 17

What is the name given to a reflected sound?

Answer 17

An echo.

Question 18

In terms of sound, what do hard surfaces do?

Answer 18

Reflect more sound and absorb less sound than softer surfaces.

Question 19

What animals can produce ultrasound?

Answer 19

Whales, bats and dolphins.

Question 20

Ultrasound has low wavelength, what does this mean?

Answer 20

They can be
-sent out in a very narrow beam
-focused on whatever is being investigated

Question 21

What is the best-known example of the use of ultra sound?

Answer 21

Medical imaging.

Question 22

Ultrasound is widely used in pre-natal scanning to check that the foetus is developing normally and to take measurements of its growth, but what measurements in particular?

Answer 22

The foetal head diameter.

Question 23

Ultrasound can be also be used on other organs or soft tissues such as the heart, kidneys, blood vessels and bladder, but why would this be?

Answer 23

To diagnose cancers.

Question 24

Aside from foetal head diameter checks and diagnosing cancers, what is another medical use of ultrasound?

Answer 24

The breaking down of kidney stones.

Question 25

What is the main industrial use for ultrasound?

Answer 25

To detect cracks or flaws in metals.

Question 26

Aside from detects defects in metals, what are some other industrial uses for ultrasound?

Answer 26

-Mapping the ocean floor in a field known as oceanography -Cleaning sensitive electronic equipment To detect layers of oil, coal, gas and other minerals deep underground.

Question 27

How can ultrasound be used in dentistry?

Answer 27

-Diagnostics: can be used to create images of the teeth and surrounding tissues, gum disease, cavities etc -Cleaning: Ultrasonic scalets use high frequency sound waves to remove plaque from teeth.

Question 28

Why does a ship use ultrasound and not ordinary sound in this device?

Answer 28

-It is easier to concentrate ultrasound into a narrow beam -Ultrasound can penetrate a greater depth of water -Smaller objects can be located or scanned.

Question 29

Who uses microwaves as radar waves for navigation?

Answer 29

Air traffic controllers, pilots and masters of large ships.

Question 30

Why can only microwaves be used as radar waves for navigation, why can’t ultrasound waves?

Answer 30

As they do not travel fast enough. To track fast moving aircraft or more distant objects.

Question 31

Give some examples of transverse waves:

Answer 31

-Water -Visible light -Gamma radiation -Ultra~violet

Question 32

What is the CREST of a wave?

Answer 32

The TOP peak.

Question 33

What is the TROUGH of a wave?

Answer 33

The BOTTOM of the wave.

Question 34

What is the name of the wavelength symbol?

Answer 34

Lambda!

Question 35

What is the relationship between frequency and period. In equation form?

Answer 35

f =1/T or T = 1/f

Question 36

What happens when ultrasound waves reach a BOUNDARY between two media with DIFFERENT DENSITIES?

Answer 36

They are PARLTY REFLECTED.

Question 37

In what ways can we use ultrasound echoes?

Answer 37

-Scanning metal castings for faults or cracks (e.g in rail tracks) -Scanning a woman’s womb to check on the development of her baby -Scanning soft tissues to diagnose cancers -Fish location by seagoing trawlers -Mapping the surface of the floor in oceanography

Question 38

In terms of measurements, what can ultrasound do? How does it show this?

Answer 38

Measure the diameter of the head of the baby as it develops in the womb. When the ultrasound reaches the baby’s head at A, some ultrasound is reflected back to the detector and produces a PULSE on the CATHODE RAY OSCILLOSCOPE (CRO). Some ultrasound passes through the head to point B, and is then reflected back to the detector. This will also produce a pulse on the CRO.

Question 39

What does the time difference (INTERVAL) between the pulses show?

Answer 39

The time it takes the ultrasound wave to travel across the baby’s head AND BACK AGAIN.

Question 40

What does SONAR stand for?

Answer 40

SOund Navigation And Ranging.

Question 41

What is SONAR used for?

Answer 41

To navigate, communicate or detect objects on or under the surface of the water, such as other vessels.

Question 42

Why would a ship use ultrasound and not ordinary sound in some cases?

Answer 42

-It is easier to concentrate into a NARROW BEAM -Ultrasound can penetrate a GREATER DEPTH of water -SMALLER OBJECTS can be located or scanned

Question 43

What does RADAR stand for?

Answer 43

RAdio Detection And Ranging.

Question 44

What is RADAR use for?

Answer 44

To track very fast objects that may be a large distance away. They are used by air traffic controllers to track passenger airliners, by the military to track missiles and by the coast guard to detect ship.s

Question 45

What can RADAR waves not be used under water?

Answer 45

The water absorbs the radar within a metre or so.