Chapter 4&5 mock Flashcards by Emily Bissett

Formula triangle for wave length

V
F Y

(Upside down y = wave length)

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Formula triangle for speed

S T

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What do waves transfer

Energy and information

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What is ultra sound

Give example

Greater than 20,000 hertz, used for scanning birth defects and manufacturing equipment

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What is infrasound

Give example

Less than 20 hertz and is used to track animals or monitor seismic activity

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What happens to waves in denser materials

They speed up and bend away from normal

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What happens to waves in less dense materials

Slows down and bends towards normal

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Name 3 characteristics of a primary wave

Fast
Compressional
Longitudinal

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Name 2 characteristics of a secondary wave

Transverse

Slower

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What can p waves travel through

Solids
Liquids
Gasses

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What can S waves travel through

Solids only

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What are sonar waves

Sonar waves are sound waves used for us to be able to “see” In water. They are waves making use of echos, the sound waves are sent off to the environment around it where the waves bounce off objects, when this happens they reflect it back.

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What can the human ear hear

20-20K hertz

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Why do they put a gel on the mums tummy before ultra sound scans

Allows scanner to move around and it acts as a medium for the waves to reflect into, more sound will be transmitted.

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What waves are released after an earth quake

Seismic waves, p then s

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What do waves transfer

Energy and information

Not matter

What is the wavelength of a wave

The distance between a point on one wage and the same point on the next wave- often easiest to measure from Crest to crest

What is the amplitude of a wave

It’s maximum disturbance from its undisturbed position

What is the frequency of a wave

The number of waves produced by a source each second or the number of waves that pass a certain point each second
Measured In hertz

What is the period of a wave

The time it takes to for one complete cycle of vibration to pass a given point

Difference between a longitudinal wave and a transverse wave

In longitudinal waves the oscillations are along the same direction as the direction of travel and energy transfer

Whereas in transverse waves the oscillations (vibrations) are at right angles to the direction of travel and energy transfer

Example of longitudinal waves

Sound waves

P waves

Examples of transverse waves

S waves
Water
Light and all other type of electromagnetic radiation

Formula for wave speed

Frequency x wavelength

What is refraction

When a wave change speed as it passes through a boundary between two substances with different densities such as air and glass. This causes them to change direction- this is called refraction.

What would cause refraction not to happen

If it crossed the boundary at an angle of 90* this is called the normal- in this case, they carry straight on.

What are som is of the effects that are a result from refraction

A swimming pool looking shallower than it actually is, bc the light coming from the bottom of the pool bends when it comes out of the surface due to refraction of light. Twinkling stars due to refraction of light A pencil partly in water appears bent at the surface of water, because the light coming from the stick bends when it comes out of the surface due to refraction of light.

What is the law of reflection

The angle of incidence equals the angle of reflection | E.g.- a wave hits a mirror at an angle of 36*, it will be reflected at the same angle 36*

Examples of reflection

Light reflecting off a mirror Scenery being reflected off a smooth water surface Seeing yourself in the mirror

Examples of waves being transmitted

Infrared light - tv remotes and can get converted into optical fibres- Which are used to carry signals, computer data and telephone calls Microwaves - transmit signals for mobile phone calls Radiowaves- transmit television and radio programs as they reflect off a charged layer in the atmosphere

Examples of waves being absorbed

Light being absorbed in the colour spectrum eg- A blue object absorbs all the colours of the spectrum except blue- it reflects blue A magenta object object absorbs all the other colours and reflects red and blue

Normal hearing range for humans

20hz to 20,000z

What are frequencies greater than 20hz called

Ultrasound

How is ultrasound used in sonar

A pulse of ultrasound is send out from ship and it bounces off the sea bed or any other objects and an echo is detected. The time it takes for these waves to travel backup indicates that depth of sea bed or object .

Uses of ultrasound in body scanning

Checking condition of foetus Investigating liver or heart problems Breaking down kidney stones Measuring blood flow in body

Explain how ultra sound is used in Foetal scanning

Ultrasound energy being reflected onto a screen to create a picture each time it passes from one material to another

What are sound with frequencies less that 20hz known as

Infrasound

Uses of infra sound

Elephants and giraffes communicate between herds over long distances, scientists use Microphones to track the herds even if hidden in dense forests Used to detect volcanic eruption Track meteors through atmosphere

What are some seismic waves

Infrasound waves