P11,P12- Waves Flashcards
What is a wave
A wave is a means of transferring energy from one place to another without a transfer of matter between the two points
What are mechanical waves
Mechanical waves are vibrations that travel through a medium
Give an example of a longitudinal wave
Sound wave
What is the difference between a transverse and a longitudinal wave
In a transverse wave, the direction of energy transfer is perpendicular to the oscillation (wobbles). In a longitudinal wave,the direction of energy transfer is the same as the oscillation (straight)
What is meant by the frequency of a wave
The number of complete oscillations or waves each second
What are the two types of waves
Transverse , longitudinal
What are the crests in a wave
The top part of the wave
What is the amplitufe of a wave
Maximum displacement of a point on the wave from its rest position
What is the wavelength of a wave
Distance between the same point on two seperate waves. May be distance between crest on one wave and crest on the other.
What is frequency in a wave repressntation
Number of complete waves passing a certain point per second. Measured in (Hz).
What is the period of a wave
Amount of time it takes for a full cycle of the wave to be completed
Period=1/frequency
How do you find speed of sound in air
Set up a signal generator thats is connectedbto a speaker. Swt the frequency to 1kHz and have two microphones at same distance from speaker connected to an oscilstor. Play sound and slowly move one microphone away from speaker and keep going until the two waves on the oscilstor are alligned up. Now the microphones will be exactly one wavelength apart so measure distsance between two microphones.
What is a ray
Straight line showing the path of a wave travels along
What can a wave do when they meet the boundsry between two different materials
Reflected, absorbed, transmitted
What are electromagnetic waves
Group of transverse waves that all travel at the same speed in a vacum
What are the waves in the electromagnetic spectrum from left to right
Radio waves, micro-waves, infrared, visible light, ultraviolet,x-rays,gamma rays
What are the three things wa wave can do at a boundary
The waves can be absorbed
The waves can be reflect
The waves can transmit through the material
If a wave slows down at a boundary what way does it bend
Towards the normal
If a wave speeds up at a boundary what direction does it bend
Away from the normal
What is a normal in waves
A straight line that is 90° to the boundary
What is refraction
When a wave reaches the boundary of two material and changes direction
What is the angle of incidence
The angle between the incoming wave and the normal
What is the angle of reflection
The engle between rhe reflected wave and normal wave
What is specular reflection
when parallel waves aare reflected in a single direction
What is diffuse reflection
When parrallel waves are reflected by a rough surface and reflected rays are scattered in different directions
What is the electromagnetic spectrum
A continous spectrum of all the possible wavelengths of electromagnetic waves
What increases when moving from left to right on the electromagnetic spectrum
Frequency increases
What increases when moving from right to left in the electromagnetic spectrum
Wavelength increases
When do electromagnetic waves transfer energy from and to
Electromagnetic waves transfer eneegy from a source to an absorber
What are gamma rays and why/how are they produced
Gamma rays are high-energy electromagnetic waves which come from changes in the nuclei of the atoms. Unstable nuclei of radioactive atoms decay and give out particles. After particles are given out the nucleus might need to get rid of extra energy and does this buy giving out gamma rays
At what speed do electromagnetic waves travel through a vacum
They all travel at the same speed
What electromagnetic waves have the longest wavelength
Radio waves
How can you produce radio waves
Using an alternating current (ac)
What are the two things radio waves are mostly used for
Radio waves are mainly used for radio and tv signals
What are radio waves sent out by and what are they received by
Radio waves are sent out by Transmitters and received by tv or radio receivers
What are the three different lengths of radio waves
Long-wave radio
Medium-wave radio
Short-wave radio
How are long-wave radio suited for their role
Long-wave radio have a wavelengths of 1-10km and therefore can be transmitted and received halfway round the world. They can diffract (bend) around the curved surface of the earth and hills into tunnels making it possible for radio signals to be received even if the recieved isnt in the line of sight of the transmitter
How are short-wave radio suited for their role what what is their role
Short-wave radio have wavelengths of around 10-100m, they dont diffract around the earths curve but can still be received at large distances from the transmitter. They are reflected between the earth and the ionosphere (an electrically charged layer in the earths upper atmosphere). Short-wave radio are used for bluetooth to send data of short distances between devices without wires.
why do radios and tv aerials have to be in line of sight of the transmitter
Because the short-wave radio doesnt bend around hills or travel far through things
What type of waves are used for communication to and from satellites and why
Microwaves because the wavelenghs of microwaves can pass easily through the earths atmosphere without being completely reflected, refracted or absorbed so they can reach satellites
Explain the process which satellites communications get sent out and received
The signal from a transmitter is sent out to space where it is picked up by a satellite receiver orbiting high above ground. The satellite transmits teh signal back to earth in a different direction where it is received by a satellite receiver on the ground
Explain how micro-waves work in a microwave to cook food
The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to the thermal energy stores of the water molecules in the food causing the water molecules to heat up. This heat is transferred to the rest of the food molecules which cooks the food
What is infrared radiation
Related to temperature. It is given out by all objects, the hotter the objects the more IR radiation it gives out. Infrared cameras can be used to detect infrared radiation and monitor temperature. If the object is hot its more red on the screen and if its cold its more purple
What do fibre optic cables do in short terms
Use visible light to transmit data
What are fibre optic cables
Thin glass or plastic fibres that carry data over long distances as pulses of visible light
Describe the structure of a fibre optic cable
Glass fibre is inside cladding ehich protects the fibre and a light ray bounces back and forth inside the fibre
What typw of radiation gives you a suntan
Ultraviolet radiation
Why are x-rays used to see if a person has any broken bones
Because x-rays pass easily through flesh however not as easy through denser material like bones so its the amount of rsdiation absorbed or not absorbed in the body that gives an x-ray image
How are x-rays and gamma waves used to treat people with cancer
High doses of x and gamma rays kill all living cells so they are directed to towards cancer cells to avoid killing too many healthy cells
What are the two things that the amount of infrared radiation emitted from an object is dependant on.
The objects temperature and the material on the surface
What is a leslie cube and what can you use them for
A hollow metal cube made out of alluminium whose four vertical faces have different surface types. e.g matt black paint, matt white paint, whiny metal and dull metal. They can be used to investigate infrared radiation emission by different surfaces.
Explain theprocess of the practical of investigating infrared radiation
Place an wmpty leslie cube on a heat proof mat and fill it up with boiling water. What a minute for the cube ti warm up then hold a themometre against each of the four faces of the cube. They should all be the same temperature. Then hold an infrared detector at 10 cm away from one of the faces and record the amount of IR radiation it detects. Repeat this for all four sides. There should be more infrared radiation on certain faces of the cube due to the type of material and colour of the face aswell
Why will more infrared radiation be detected around a black face of a leslie cube
Black absorbs more infrared radiation
How can UV radiation be harmful to humans
UV damages surface cells which can lead to sunburn and cause skinnto age prematurely. Other effects can be skin cancer
what can x-rays and gamma rays cause and why
They are both types of ionising radiation (they carry enough energy to knock electrons out of atoms) which cause gene mutation or cell destruction and cancer
How can you measure risk of electromagnetic waves
You can measure risk by using radiation doss in siverts
What way do the magnetic field lines go in a magnetic field
They always go from north to south
What does the distance between each magnetic field line tell us
The closer the lines are the stronger the magnetic field, the further away you get the weaker the field is
What are the two different types of forces
Attractive forces and repulsive forces
What are the teo types of magnets
Permanent magnets and induced magnets
What are permenant magnets
Magnets that produce their own magnetic field
What are induced magnets
Induced magnets are magnetic materials thsn turn into magnets when put into a magnetic field
What is the force between permenant and induced magnets
The force is always attractive
How can you increase the strength of a magnetic field that a wire produces
By wrapping the wire into a coil and a solenoid
If the field lines are closer together in a magnetic field what does that mean
The force is stronger
What is a solenoid with an iron core called
An electromagnet
