Waves (Unfinished) Flashcards
What type of waves are EM waves
Tansverse waves
EM waves characteristics
They travel at the same speed through a air vacume, they travel at the speed of light in a vacume, they travel slower in solids
Wave length of x-rays
10^-10 m
What happens to the wave length and frequency as you go down the EM spectrum
Increasing frequency and decreasing wavelength
Why is there such a large range of frequencies in EM wave spectrum
EM waves are generated by a variety of changes in atoms and their nuclei
Frequency of X-rays
10^17 hz
What is refraction
When waves crosses a boundary between materials at an angle it changes a direction
What effects refraction
How much the wave speeds up or slows down which usually depends on the density of the materials.
What directions do waves bend in refraction
If the wave slows down it will bend towards the normal
If it crosses into a material and speeds up it will bend away from the normal
What happens to the frequency when the wave length changes in refraction
It stays the same
What is the optical density
A measure of how quickly light can travel through, the higher the optical density, the slower light waves travel through it.
What does the angle of incidence always equal
the angle of refelction
How are radio waves made
By oscillating charges and magnetic fields
What does the frequency of the waves produced be eqaul to
The alternating current
What are radio waves used for
Mainly for communication
Long radio waves (1-10km) can be transported half way around the world.
How can short radio waves be transported long distances
Short radio waves (10-100m) can be recieved at long distances from the transmitter as they are reflected from the ionosphere.
Medium wave signals can also be reflected from the ionosphere depending on the atmospheric conditions
What type of video waves are used for TV and radio
Very short wavelengths
What are microwaves used for
Used by satalites for communication
Mircowave ovens
How does microwaves trasmitt from space
It’s signals on a transmitter is transmitted into space where it’s picked up by Saturday receiver dish orbiting and transmits the signal back to a satellite dish on the ground
How are microwaves used in the microwave ovens
Microwaves are absorbed by water molecules in food. The microwave penetrate after a few centimetres into the food little been dissolved and transfers energy to the carrying to the water molecules which then transfers the energy around
How can infrared radiation be used
To increase or monitor temperature
What can infared radiation be used for
Detect infrared radiation and monitor the temperature. The camera to text the IR radiation and turns it into an electrical signal
How can food be cooked by IR radiation
Absorbing IR radiation causes objects to get hotter
How was IR radiation used in electric heaters
Electric heaters contain a long piece of wire that heats up when a current flows through it. The wire that emits a lot of infrared radiation which is absorbed by objects in the air in the room, it is then transferred into thermal energy stores
How do fibre optic cables use visible light to transmit data
Optic fibres are thin glass or plastic fibres that can carry data every long distances as poses of visible light through reflection of the light rays about and forth until we reach the end of the fibre
How does ultraviolet radiation create flurocent lights
Fluorescent lights generate UV radiation which absorb and re-emitt as visible light by a layer compound called phosphor on the inside of the bulb.
How is UV radiation used in security pens
On the UV light the ink will blow if it is fluorescent but is invisible otherwise
How is UV radiation used for suntan
Ultraviolet radiation is produced by the Sun and exposure gives people a suntan, you can use UV lamps to give an artificial suntan however exposure can be dangerous
How are x-rays used in medicine
X-rays can be used by radio glasses to take photos to see bones or metal
How do x-rays work
X-rays pass easily through flesh but not through denser material like bones or metal.
How x-rays and gamma rays used in medicine
Radiographers use these raised to treat people with cancer good radiotherapy. This is because I doses of these rays kill a living cell so they are carefully directed towards cancer cells
How is gamma radiation used as a medical traser
This is where a gamma emitting source is injected into a patient and its progress is followed around the body. Gama radiation is well suited as it can pass out through the body to be detected
How can EM radiation be harmful
High frequency waves Such as UV rays x-rays and gamma rays or transfer lots of energy so can cause lots of damage. UV radiation damages surface cells which can lead to sunburn it can cause skin cancer. X-rays and gamma rays are types of ionising radiation which mutates or destroys cells and causes cancer
What is ionising radiation
Radiation that produces from an ion as it has enough energy to displace an electron from an atom
The speed of light speed
3.0 x 10^8 m/s in a vacuum.
What does the particles of a medium do in waves traveling through a medium
The particles oscillate and transfer nergy between eachother
What is the amplitude of a wave
The maximum displacement of a point on the wave from its undistured position
What is a wavelength
The distance between the same point on two adjecent waves
Wha is the frequency of a wave
The number of complete waves passing a certain point per second. It is measured in hertz
What is the equation for a period (amount of time it takes for a full cycle) of a wave
Period = 1/frequency
What are the characteristics of transverse waves
There are waves that have sideways vibrations. The oscillations are perpendicular to the direction of energy transfer. Less waves are transverse including electromagnetic waves, ripples and waves in water, a wave on a string.
Longitudal waves
The oscillations are parallel to the direction of energy transfer. Some examples of sound waves in air, ultrasound or shockwaves
Wave speed equation
Wave speed = frequency x wavelenght
How can you use an oscilloscope to measure the speed of sound?
Set up the telescope to detect waves each microphone showing a separate waves. Start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the display but have moved exactly one wavelength apart. That of the distance between the microphones to find one wavelength.You can use the equation to find the velocity from frequency and wavelength, The frequency is whatever you set the single generator to. The speed of sound in air is around 330 m/s
What happens when waves arrive at a boundry betwen two different materials
- the waves are absorbed by the material
- the waves are transmitted often leadin gto refraction
- the waves are reflected
equation for angle of incidence
= angle of reflection
What is the angle of incidence
The angle between the incoming wave and the normal
What is the angle of reflection
The nalge between the reflected waveand the normal
What is the normal line
An imaginary line that is perpendicular to the surface at the point of incindence
What is specular reflection
Happens when waves is reflected in a single direction by smooth surface.
What is diffuse reflection
When a wave is reflected by with surface and the reflected rays are scattered in lots of directions
Why do diffuse rays scatter in different direction
The normal is different for each income in a way which means that angle of incidents is different for me to me
How do different colours vary in characteristics
Each colour has its own narrow range of frequencies and wave lengths ranging from violets dow at the 400nm to reds at 700nm
What do opaque objects do
They do not transmit light. When visible light waves hit them via the tube some wavelengths of light reflect others
What does collour and transparency depend on
Absorbed wave lengths.
Hat is ghe difference with black and white objects with light
White objects reflect
Black objects absorb
What objects transmit light
Tranparent and translucent objects
What is translucent and transparent colour depend on
Waves lengths of light transmitted and reflected by it
What do colour filters do
Only let through particular wavelegths whch filter out different wavelegths of light so only some colours are transmitted - the rest are absorbed
What happens to a colour if it is not the right colour filter
Any colour but the right colour looks black
What is a perfect black body
An object that absorbs all of the rediation that hits it. No radiation is reflected or transmitted. They are the best possible emmitters
What does the intensity and distribution of wavelengths emitted by an object depend on
The object’s temp (as the temp of an object increases the intensity of every emitted wavelegnth to decrease
How do vibrations cause sound waves
Vibrations of an object are passes through the surrounding medium as a series of compressions and rarefractions
What can humans hear in sound range
20 Hz to 20 kHz
How can the ear hear sound
Vibrate. These vibrations are passed on to tiny bones in your ear called assistance through the semicircular canals to the cochela The tenancies vibrations into electrical signals which gets into the brain
When would sound waves reflect and refract
Spund waves reflect by hard flat surfaces. Sound waves refract as they enter different media.
What happens to sound waves in denser materials
The speed up because when a wave travels into different medium its wavelength changes is the same so the speed changes
What iis ultra sound
Sound waves beyond the range of humans hearing higher than 20,000 Hz
What is a partial reflection
When a wave passes from one medium to another some of the wave is reflected off the boundary between the two media and some is transmitted
How is ultra sound useful
Medical imagining and industrial imaging
Ultrasound waves can enter materials or pass through a body
How can you detect seismic waves
Earthquakes produces sismic waves which travel out through the earth. We can detect these waves usning sismometers to work out the time it takes for the shock waves to reach the seismetere.
What is the movment of sismic waves through different layers
When seismic waves meet your country between different days of the material inside the Earth some waves as I will be reflected. Most of the time if the weather is affected the change in curved path. But when properties change suddenly the wave speed changes abruptly and the path as a kingk
What are the two different seismic waves
P waves and S waves
How can you use seismic waves
Bob serving outside affected scientists have been able to work out where the properties of the Earth changed. Our understanding of the internal structure of the Earth and size of that of course is based on observations
P waves
Longitdal waves that move fast through solids and liquids and faster than s waves
S waves
Are transverse and can’t travel through liquids
