Chapter 4 Mock Flashcards by Emily Bissett

What do waves do

Transfer energy and information without transferring matter

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What happens when a light wave goes through something more dense

Slows down and bends towards normal

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What happens to a light wave when it goes through something less dense

It speeds up and bends away from the normal

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How to measure velocity of air

Someone stand for away and make a loud banging noise and time how long it takes for someone in another place to hear it

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Speed of sound

340

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What is the wave length

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

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What is frequency in terms of waves

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

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What is the period of a wave

The time it takes to complete one full oscillation

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What is the amplitude of a wave

Maximum disturbance from its undisturbed position

From centre line to top of crest or bottom of trough

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What is the velocity of a wave

Number of wave passing a given point at a given time

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What is a longitudinal/ P wave give characteristics and example

Can travel through liquids and solids&;gasses
Vibrations In same direction (parallel) as the direction of travel
Seismic
Fast
E.G. SOUND

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What is a transverse/ S wave give characteristics and give me an example

Vibrations are at right angles to the direction of travel
Slow
Travel through solids only
E.G. ALL THE WAVES IN ELECTROMAGNETIC SPECTRUM AND WATER

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Equation for wave speed

v = f x λ

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What does this symbol stand for - λ

Wave length

It’s called a lambda

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What is sound with frequencies of greater than 20,000 hertz known as

Ultrasound

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What is Sound with frequencies less than 20 hertz know as

Infrasound

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What is the range of frequencies humans can hear

15-18,000 hertz

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How to measure velocity of sound in air

2 people apart and a certain distance
One bangs two blocks together
As soon as you see the blocks hit each other start the stop watch and stop it when u hear a sound
Calculate the speed by dividing the distance and the time
To eliminate human error use a computer timed method with two sound activated switches

Practical to measure velocity of ripples on water surface

Use a ripple tank and fasten a ruler on the sides so you can see markings above water level. Put a sheet of white paper underneath, reflection of water on sheet makes easier for counting
Count how many waves formed in 10s
Look at waves against ruler to estimate wave lengths of waves, to make it more accurate take a photo of waves with ruler in.
Mark 2 points on the edge of the ripple tank and measure the distance and use a stop watch to find out how long it takes from a wave to go from one mark to the other

How to calculate depth or distance from time and wave velocity

Use the distance = speed x time triangle and double answer if it’s asking for there and back

What are the effects of reflection

Sound and light waves reflect from surfaces. When they reflect they obey the law of reflection (the angle of incidence equals the angle of reflection)
Smooth surfaces eg mirrors are good clear specular reflectors whereas rough surfaces scatter sound and light in all directions by disuse reflection.

What are the effects of refraction

Sound and light waves change speed when they pass across the boundary between 2 substances with different densities such as air and glass. This causes them to change direction and this effect is called refraction.

What happens in refraction if the boundary is at an angle of 90

The line carries straight on

What are the effects of transmission

Energy in a wave is transmitted through a pulse in wave from a less dense medium and at the boundary moves to a more dense medium. They move through materials without being absorbed
Eg- radio waves are used to transmit television and radio programs

What are the effects of absorption

Absorption transfers its energy to the material it penetrates Eg- sand is hot as it absorbs electromagnetic waves from the sun Absorption of light to see colour

What colour will an object be if all wavelengths are reflected equally

White

What colour will the object he if all the wavelengths are absorbed

Black

How does human ear receive sound

The eardrum is connected to a hammer, movements and vibrations of war drum will set the hammer, anvil and stirrup into motion at the same frequency of the sound wave. The three tiny bones of the middle ear act as levers to amplify vibrations of the sound wave.

Uses of ultrasound in ships and submarines

Called Sonar- used on ships and submarines to detect fish or seabed. A pulse of ultrasound is sent out from the ship, it bounces off the object and echo is detected, the Tim taken for wave to travel indicates the depth of the object

Uses of ultrasound In foetal scanning

Ultrasound energy being reflected each time it passes from one material to another(boundaries between different tissues and organs) every time it reflects an image is created On a screen. A watery jelly is used as the jelly reflects more sound so u have a clearer view, whereas the air would reflect the sound.

Why shouldn't their be any air bubbles in the jelly of an ultrasound

So none of the sound is reflected in the air which give an inaccurate view

Why do metal objects show up in ultrasound scans

They are dense so reflect a picture

Why are ultrasound scans used instead of x rays for scan of a baby

Don't damage living cells | Procure image of soft tissue

Another example of a medical use of an ultrasound

Breaking down kidney stone with Hugh powered ultrasound waves. The stones vibrate until the shake themselves apart and are then easily passed out of the body via the urethra

Uses of infrasound

Communicating over long distances- elephant herds Detecting volcanic eruptions Tracking passage if meteors

Use of ultra sound for exploring the earths core

When seismic waves pass through earth they refract or bend. Speed of seismic waves depends on densities. Core has a depth of 2900km and is composed of iron. We know it exists because it refracts seismic waves- creating a shadow zone. Outer part of core = liquid as seismic waves don't pass through it

What happens when sound waves (p waves) travel through materials

Speed up in denser material and bend away from the normal

What happens to wavelength in denser and less dense material

Dense=The wavelength increases | Less dense= The wavelength decreases (shorter)

What happens to light waves (s waves) as they travel through materials

The slow down in dense materials and bends towards normal

What is total Internal reflection

In optical fibres (thin high quality glass)

What is total internal reflection

Found in optical fibres (small thin glass) when light tries to move from glass to air at a greater angle than the critical angle the refracted ray cannot escape the glass. Total internal reflection occurs inside class and is called total because all the light must be reflected as it travels down rod/fibre

Uses of optical fibres

Endoscopes- surgeons see inside patient They carry enormous amounts of information as pulses as Light - more info than copper cable tv lines. High speed communications, e.g. Cable tv and high speed broadband services.

Why do we use jelly on stomach of pregnant women when using an ultrasound

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