Waves

wave

a ___ is a transfer of energy through vibrations

wave

a ___ is a disturbance or oscillation that travels through space and time, accompanied by a transfer of energy

displacement

movement in a particular direction

transverse waves

when the vibrations/displacement Is perpendicular to the direction of the wave

longitudinal waves

when the vibrations/displacement is parallel to the direction of the wave

transverse waves

Particles move up and down

longitudinal waves

particles move back and forth

electromagnetic waves

transverse wave example

sound waves

longitudinal wave example

electromagnetic wave

- An ___ ___ can be created by moving charges through electrical or magnetic means by giving them energy, radioactive decay etc.

- moving charges back and forth will produce an oscillating electric and magnetic fields which travel at the speed of light.

Electromagnetic waves

___ ___ do not need particles to carry vibrations.

e.g. light and heat from the sun reach us through the vacuum of space.

mechanical waves

___ ___ need matter to transfer energy.

e.g. waves on a slinky, sound waves, water.

transverse, longitudinal

___ (s) and ___ (p) waves are also caused by earthquakes. S waves vibrate side to side as well as up and down. P waves compress and expand the ground.

Amplitude

___ is 'how high' the wave is - the highest displacement.

Wavelength

___ is the distance between two corresponding points on a wave and is measured in metres. It can only be found on a distance in m graph.

Time period

___ is the time it takes for one wave to pass and is measured in seconds. It can only be found from a time graph.

frequency

___ is how many waves pass by every second and is measured in hertz.

Amplitude, frequency

Sound as a wave

____ is loudness

____ is pitch

High wavelength

Quiet sound (low amplitude), low frequency/ pitch - ____ ____

low wavelength

Quiet sound (low amplitude), high frequency/pitch - ___ ___

High wavelength

Loud sound (high amplitude), low frequency/pitch - ___ ___

low wavelength

Loud sound (high amplitude), high frequency/pitch - ___ ___

wave speed = frequency x wavelength

the wave equation

Oscilloscopes

___ are a way of displaying electrical signals e.g. an ECG

verticle

To find the voltage from an oscilloscope you read the ___ axis and multiply that value by the voltage setting/dial.

horizontal

To find the time from an oscilloscope you read the ___ axis and multiply by the timebase.

Interference

when two or more waves superimpose to form a resultant wave of greater or lower amplitude

adds up

constructive interference...

cancels out

destructive interference...

constructive interference

when peaks meet peaks and troughs meet troughs, the waves are in line so they add up to equal a bigger wave.

destructive interference

when peaks meet troughs, the waves are out of line so they cancel out.

in a constant phase difference, monochromatic

conditions to set up a clear interference pattern, the waves must be coherent:

- ___ ___ ___ ___ ___

- ___

Diffraction

when waves spread out from the edge of a gap

interference

when two or more waves interact with one another to form a pattern

size of the gap is similar to wavelength

more diffraction if the ___ ___ ___ ___ ___ ___ ___

wavelength is increased (or frequency decreased)

more diffraction if ___ ___ ___

resonance

when you increase the amplitude of a wave by making it oscillate (vibrate) at the right frequency

doppler shift

the difference between the transmitted and received frequencies.

higher

if the sound is moving towards you it will be a ___ pitch.

lower

if the sound is moving away from you it will be a ___ pitch

towards

if the sound is moving ___ you it will be a higher pitch

away

if the sound is moving ___ from you it will be a lower pitch

blue

if the electromagnetic wave is moving towards you it will be shifted to the ___ end

towards

if the electromagnetic wave is moving ___ you it will be shifted to the blue end

red

if the electromagnetic wave is moving away from you it will be shifted to the ___ end

away

if the electromagnetic wave is moving ___ from you it will be shifted to the red end

light

___ vibrates at lots of different angles

specular reflection

The reflection of waves in one direction produced by a smooth surface

diffuse reflection

The reflection of waves in many directions from a rough surface

law of reflection

1. angle of incidence = angle of reflection

2. Incident ray, reflected ray and normal are all in the same plane (flat/2D)

1. The angle of incidence = angle of reflection

2. The incident ray, the reflected ray and the normal are all in the same plane

law of reflection

reflection

The law of reflection states that the angle of ___ is always equal to the angle of incidence. Both angles are measured relative to the normal, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

normal

The law of reflection states that the angle of reflection is always equal to the angle of incidence. Both angles are measured relative to the ___, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

ninety

The law of reflection states that the angle of reflection is always equal to the angle of incidence. Both angles are measured relative to the normal, a line that is ___ degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

virtual

The law of reflection states that the angle of reflection is always equal to the angle of incidence. Both angles are measured relative to the normal, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a ___ image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

real

The law of reflection states that the angle of reflection is always equal to the angle of incidence. Both angles are measured relative to the normal, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a ___ image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

size

The law of reflection states that the angle of reflection is always equal to the angle of incidence. Both angles are measured relative to the normal, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same ___ and way up as the object.

equal

The law of reflection states that the angle of reflection is always ___ to the angle of incidence. Both angles are measured relative to the normal, a line that is ninety degrees to the reflecting surface at the point of reflection. A plane mirror forms a virtual image which is unlike a real image in that it cannot be cast onto a screen. The image in the plane mirror is also the same size and way up as the object.

convex mirror

The reflected image is smaller and upright because the reflected light rays do not cross the focal point.

concave mirror

The image reflected image is inverted because the light rays intersect at the focal point before being imaged. The size depends on how close the object is to the mirror.

refraction

light will change speed and direction (if it is not coming head on) when it goes from one medium to another.

towards the normal

As the ray enters the glass from the air, it changes direction ___ ___ ___. The angle of refraction is less than the angle of incidence.

less

As the ray enters the glass from the air, it changes direction towards the normal. The angle of refraction is ___ than the angle of incidence.

coming head on

light will not refract when ___ ___ ___.

medium at an angle

The ray only changes direction if it enters the ___ ___ ___ ___. If it enters head on (angle of incidence = 0) it will slow down but be undeviated.

travel in straight lines

We perceive light to ___ ___ ___ ___, so when looking at something in water it appears to be closer than it actually is.

Law of Refraction

1. when a ray will change speed and direction as it travels from one medium into another.

2. snell's law (not assessed)

3. incident ray, refracted ray and normal are all in the same plane (i.e flat or in 2D)

angle of incidence

the angle between the incident ray and the normal

angle of refraction

the angle between the refracted ray and the normal

electromagnetic waves similarities

- all are a disturbance or oscillation that travels through the electric and magnetic field (as well as space and time)

- they are all a transfer of energy

- they all travel at 3x10 to the power of 8 m/s (velocity of light)

- they can all travel through a vacuum

electromagnetic waves differences

- wavelength and frequency

- different effects of absorption based on frequency (i.e. energy) e.g radio waves are safe but gamma rays are not.

electric current

radio waves and microwaves can be absorbed by metals to make an ___ ___ e.g radio signals from your tv, phone signal.

heating effect

microwaves and infra red waves cause particles to vibrate more causing a ___ ___.

chemical changes

visible and UV light can be absorbed by molecules making them more likely to react chemically. e.g photosynthesis, the ozone layer, your retina.

Ionisation

UV, X-rays and gamma rays carry enough energy to cause and electron to leave an atom. The resulting particle is charged and is called an ion which reacts very easily. ___ damages living cells.

radiowaves

used mainly for communication

radiowaves

1. An alternating current is fed into a transmitter

2. make the electrons in the metal transmitter aerial oscillate

3. which produces ___

4. which make electrons in the metal receiver aerial oscillate

5. and a matching alternating current comes out of the receiver

Radiowaves

an electromagnetic wave that has the longest wavelength and has the least energy

Radiowaves

___ cause electrons in an antenna to vibrate

microwaves uses

- for cooking food rapidly

- satellite transmission

- mobile phone communications

microwaves

Electromagnetic waves that have shorter wavelengths and higher frequencies than radio waves.

radiowaves and microwaves

produced by an alternating current

Infrared

electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves

Infrared

- otherwise known as heat radiation

- is given off by all hot objects

- we feel it on our skin as radiant heat

Infrared

used for night vision equipment and in remote controls for TV's.

Infrared

firefighters use ___ cameras when going into buildings full of smoke to see heat signatures of anyone who is trapped or injured.

visible light

the only electromagnetic waves that are visible to the human eye

visible light

___ ___ is used to send signals (traffic lights), and in optical fibre digital communications.

visible light

___ ___ can be made from chemical reactions (chemiluminescence), nuclear fusion, current in a wire.

ultraviolet

- detects forgeries and hidden security markers (fluorescence) e.g. money.

- kills insects, some are drawn to lights because they use it as a navigational guide (not mosquitoes)

ultraviolet light

___ ___ makes your teeth, fingernails and some clothes glow because they contain phosphors which are substances that emit visible light in response to radiation.

ultraviolet light

___ ___ gives you a suntan, ___ ___ from the sun hits the skin and some produces vitamin D, but it is also ionising so can kill cells causing the body to produce extra melanin which can cause skin cancer.

sunbeds

___ damage your skin each time you use them, ages the skin and can lead to to skin cancer. Using one once or more per month can increase the risk of skin cancer by more than half.

ultraviolet

When a current is passed through a gas tube electron transitions occur. The transitions release photons of ___ light. The ___ light causes transitions in phosphors which release photons of visible light. We cannot see ___ light, what we see is the light that has been released from the phosphors.

Phosphors

When a current is passed through a gas tube electron transitions occur. The transitions release photons of ultraviolet light. The ultraviolet light causes transitions in ___ which release photons of visible light. We cannot see ultraviolet light, what we see is the light that has been released from the ___.

x-ray uses

- detect broken bones

- to screen bags at airports for bombs, guns etc

- used to look inside the coffin of a mummy without opening it

X-ray production

- electrons jump across from the heated filament (cathode) to the tungsten target (anode) due to the very high potential difference between them

- electrons can be slowed down or deflected to release continuous x-rays

- or electrons can cause transitions in the tungsten atoms to release characteristic x-rays

gamma ray uses

- help in the diagnosis and treatment of cancers

- sterilise medical equipment

Gamma

things decay to become more stable. They decay so that they have a more stable ratio of protons and neutrons, in other words, closer to the stability band. ___ can be released after radioactive decay.

protons and neutrons

things decay to become more stable. They decay so that they have a more stable ratio of ___ ___ ___, in other words, closer to the stability band. Gamma can be released after radioactive decay.