P12 - Wave properties

What are mechanical waves?

Vibrations travel through a medium

What are electromagnetic waves?

Travel through a vacuum

What are the two types of waves?

• Electromagnetic

• Mechanical

What happens to the substance as the waves travel?

The substance does not move

What are transverse waves?

Oscillations that are perpendicular to the direction of energy transfer

What are longitudinal waves?

Oscillations are parallel to the direction of energy transfer

What time of waves are mechanical waves?

Transverse of longitudinal

What type of waves are electromagnetic waves?

Transverse

What are the parts of a wave?

What is the amplitude?

Max. Displacement of a point on a wave from its undisturbed position

What happens to energy as amplitude increases?

The energy it carries increases

What is the wavelength?

Distance from a point of a wave to an equivalent point in the adjacent wave

What is frequency?

The number of waves passing a fixed point

What is the formula for period and frequency?

Period (s, seconds) = 1/frequency (Hertz, Hz)

What are plane waves?

Straight waves that all move at the same speed or stay at the same distance apart

What is the speed of a wave?

The distance a wave travels in a second

What is the equation for wave speed, frequency and wavelength?

Wave speed (metres per second, m/s) = Frequency (hertz, Hz) x wavelength (metres, m)

What is a wavefront?

Lines used to represent the vibrations

how are plane waves produced in ripple tanks?

By dipping a ruler in water

What are incident waves?

Waves reflected by the barrier

How do reflections occur?

When the wavefront of an incident ray is not parallel to the barrier

What is a refraction?

Change of the direction waves travel when they cross a boundary

What happens to waves at a non-zero boundary to another medium?

Waves change direction

What happens to waves perpendicular to the boundary to another medium?

Waves do not change direction but change speed

What happens to the waves if the wavefront travels slower in a new medium?

Their waves are closer together and at a smaller angle to the boundary due to the waves traveling at different speeds

what do materials determine of a wave?

Whether it is reflected or absorbed

What happens to a material and the wave of a wave is absorbed?

The material gets hotter as it is gaining energy while the amplitude of the wave decreases as the substance absorbs the energy

How is sound heard?

By vibrations vibrating the next layer of air causing vibrations to be sent out and reach your ears which vibrates the eardrum

How is an echo formed?

Soundwaves reflect from smooth, hard surfaces

How do you measure the speed of water using a lamp?

• The signal generator attached to the dipper of a ripple tank creates water waves at a sad frequency

• The lamp shows the wave crest on the screen making sure the waves on the screen are the same size as the ones on the water

• The distance between each shadow line is one wavelength

• Measure deck distance of 10 wavelengths and divide by 10 for the average wavelength by taking a photo

• Use V = f x wavelength to Calculate the wave speed

How do you find the speed of waves using string?

• Attach a Signal generator to the vibration Inducer

• Attach a stretch string to the vibration transducer and pulley attached to a clamp with a mass at the bottom

• Turn on the signal generator and vibration inducer so the strings start vibrating

• Adjust the frequency wave is produced

• Measure the amount of wave lines and the distance between them and divide them to get the main half wavelength

• You can get the full wavelength by multiplying

• The frequency is the generator to

• You can use v = f x wavelength for speed

Why does music sounds nice to listen to?

It’s sound waves change smoothly and the wave pattern repeats regularly while general noises have frequencies without patterns

What frequency can the human ear detect?

20Hz to 20,000 Hz

Why is there a limited frequency for hearing?

Soundwaves change into vibrations and solids, but only which only happened in limited frequencies

How does the wave change from the Air to the ear?

The frequency of the wave doesn’t change, but the wavelength does

What is echo pulsing?

Using pulses of high frequency sound waves to detect objects in deep water to measure the water depth

How does echo pulsing work?

Pulses from the transmitter are reflected at the same depth as the transmitter and the time is measured

How is the total Distance calculated in Echo pulsing?

½ x V x t

What is a carcinogen?

Can cause cancer

What is ultrasound?

Soundwaves above the audible frequency

what is ultrasound used for?

To see the inside of the womb or organs or metal castings

What does the ultrasound scanner have to see organs?

Transducer, a control system and the display system

What is a transducer?

Electronic device placed on the body which detect pulses of an ultrasound

How does ultrasound detect inside the body?

The pulses partially reflect from different tissue boundaries and return to the transducer as a sequence arriving a different times

What are the advantages of ultrasound?

They reflect at boundaries between different types of tissue to see organs and soft tissues

They are non-ionising which means they do not have enough energy to remove an electron to ionised atoms

What is a flaw in metal?

Internal cracks and metal Castings

How do ultrasound waves detect flaws?

Ultrasound waves can reflect from the flow in the metal, so the transducer against the waves as they are picked up by the oscilloscope

How do you calculate a distance travelled by ultrasound?

Distance travelled = speed of ultrasound x time

When does an earthquake happen?

When forces in the earth increase and becomes strong enough and move layers of rock

What is seismic waves?

Energy transferred from earthquakes, create shock waves that travel through the earth

Where are earthquakes generated?

In the crest

What is the structure of the inside of the earth?

What is the crust?

Solid layer of rock

What is the mantle?

Thicker layer of molten rock

What is the origin?

The point where the earthquake generates

What is the epicentre?

Nearest point on the surface of the focus

What is a seismometer?

Detector detect earthquakes

What are three types of seismic waves?

Primary waves - initial tremors lasting one minute

Secondary waves – cause more tremors later

L waves – last and cause of violent movement on the surface upward And downward and back-and-forth

What are P-waves?

Longitude waves as they push materials back-and-forth

What are S waves?

Transverse waves as they shake materials while passing side to side

How fast are the different types of waves?

P-waves are fastest than S waves and out waves

What happens when waves travel through the mantle?

P-waves and S waves change direction as the speed and depth change

How does the P-wave travel through the Earth?

Pee-wee the fact that the boundary from mental and outer core As Speed changes

How do S waves travel through the Earth?

As waves are transfers so they cannot travel through the liquid outer core

What does seismometers record?

Some seismometers only record out waves as they are in the shadow zone where no P waves or S waves are recorded

What is the shadow so tell us about the inside of the Earth

Shadow zone shows that there is a liquid outer core under the mantle as pews are refracted at the boundary. As The second refraction is down the way cannot reach the shadow zone.

What do S waves tell us about the inside of the earth?

S waves cannot travel to the outer core as they can’t travel through liquid

What do we P-wave show about the inside of the earth?

We P waves show that there is a solid in cord that reacts P-waves into the shadow zone

How is the boundary between the Crust and Mantle Found ?

When the speed of Seismic waves changed at around 50 km

How can ultrasound be used medically

To remove kidney stones

repair damage, tissues

Remove plaque teeth

Why are x-rays better than ultrasound?

They have higher quality

can be done in any direction

Any part of the body

Easier to see a problem

Once scientist find that ultrasound is bad. What should they do?

Published their results to the public