Topic P6 Waves Flashcards
how do waves transfer energy
from one place to another without transferring any matter
what is amplitude of a wave
the maximum displacement of a point on the wave from its undisturbed position
what is the wavelength
the distance between the same point on 2 adjacent waves
what is the frequency
the number of complete waves passing a certain point per second
what is frequency measured in
hertz (Hz)
what is period measured in
seconds
what are transvervse waves
-have sideways vibrations
-they’re perpendicular at the direction of energy transfer
waves are either
-transvervse
-longitudinal
state which waves are transvervse
- electromagnetic waves
- ripples and waves in water
- a wave on a string
what are longitudinal waves
-oscillations are parallel to the direction of energy transfer
an example of a longitduinal wave
-air
what is wave speed measured in
m/s
what is wavelength measured in
metres
what should you use an oscilloscope to measure
-to measure the speed of sound
1. set it up so detected waves are shown as seperate waves
2. both microscopes next to the speaker and then slowly move 1 away until next waves are aligned
3. measure distance between the microphones to find 1wavelength
state what happens when waves meet boundaries
- absorbed by 2nd material
- **transmit **through 2nd material
- wave is **reflected **
what type of waves are electromagnetic
transverse
-they transfer energy from a source to an absorber
how does a camp fire transfer energy
-by emitting infared radiation
-they are then absorbed by objects to the thermal energy store
how do radio waves transfer energy
to the kinetic energy stores of electrons in radio receivers which generates an electrical current
state characteristics of electromagnetic waves
-all travel at the same speed through air
-aren’t vibrations of particles and are vibrations of electric and magnetic fields means TRAVEL THROUGH VACUUM
-vary in wavelength
what is refraction
where waves change direction at a boundary
state how u detect refraction
when a wave hits the boundary at an angle and changes direction
how ray diagrams show the path of a wave
-straight lines that are perpendicular to wave fronts and they show the direction a wave is travelling in
state how refracted waves slow down or speed up
-when the waves bends towards the normal, it slows down
-when it bends away from the normal it speeds up
how to construct a ray diagram
for a refracted light ray
learn how to do a ray diagram
how are radio waves made
by oscillating charges
-alternating currents are made up of oscillating charges
what are radio waves mainly used
for communication
how are microwaves used by satellites
-communication to and from satellites use microwaves
-its best to use microwaves which can pass easily through the Earth’s watery atmosphere
-the signal from a transmitter is transmitted into space
-the receiver dish orbits thousands of km above earth
-satelite transmits the signals back to earth
explain how microwave ovens use microwaves
-in microwave ovens the microwaves are absorbed by water molecules in food
-the microwave penetrates up a few cm into the food before being absoorbed and transferring the energy
-water molecules then transfer energy to the rest of molecules in food by heating, quickly cooking food
how can infrared radiation be used to increase temperatures
-infrared cameras are used to detect infrared radiation and monitor temperature
-the camera detects the IR radiation and turns it into an electrical signal which is displayed on a screen
-the hotter the object is the birghter it appears
explain how electric heaters heat a room
-they contain a long piece of wire that heats up when a current flows through it
-wire then emits infared radiation
-this is then absorbed by objects and energys transferred by the IR waves to thermal energy stores
what does fibre optic cables use
visible light to transmit data
-they carry data from telephoes over long distances as pulses of visible light
-work bc of reflection
what are ultraviolet radiation used for
-gives you a suntan
-fluorescent lights generate UV radiation which is then re-emitted as visible light by phosphor on the inside of a bulb
-energy efficient and are good to use when light is needed
state why we use X rays
-for medicine
-they pass easily through flesh but not as easily through dense materials like bones or metal
what are radiographers used for
-X rays and gamma rays to treat people with cancer
state the dangers of using electromagnetic radiation
-they enter living tissues, and is often harmless but sometimes creates havoc
-UV radiation damages surface cells, leading to sub burn and can cause blindness and an increased risk of skin cancer
-high fequency waves like UV transfer lots of energy + cause lots of damage
state how to measure risks by using radiation doses in sieverts
-by radiation doses, which is measured in sieverts
