GCSE Triple Science P6: Waves (Properties of waves (Waves transfer energy…
GCSE Triple Science P6: Waves
Used in long-range communication and radio
Radio waves diffract around large objects because they have the same wavelength as those objects
Used in long range communication because they reflect off the ionosphere to a location insteacd of being transmitted through it, so the message can get to the reciever.
Microwaves are used for communication with satellites and in microwave ovens.
-Satellites because they transmit through the ionosphere unlike radio waves.
-Microwave ovens because they are absorbed by fat and water and have a heating effect when concentrated in one area.
Used in thermal imaging/guns (for example, police using it to track someone) and in fibre Optic cables.
-thermal imaging because everything emits infrared light so everything would be visible.
-Fibre Optic because infrared has the right wavelength for total internal reflection to occur in the cables.
~10^-5 m wavelength
Also used in Fibre Optic because it has the right wavelength.
~0.5*10^-8 m wavelength
Used in: Crime scene investigation, killing pathogens and tanning beds.
Causes sunburn. is also on the ionising end of the EM spectrum.
10^-8 m wavelength
Used in X-ray imaging of bone structure because they are absorbed by soft tissue but reflected by hard tissue. Reflected X-rays are picked up by a reciever and turned into an image.
Can cause cancer. (~800 per year from X-ray imaging).
10^-10 m wavelength
Used in radiotherapy and medical imaging.
-Radiotherapy because it kills cancer cells when concentrated in an area. Usually directed at a tumor with different angles so as not to kill healthy cells.
-In imaging, a patient is given a radioactive meal and put in a gamma camera which can map the radiation moving around the patient's system, making an accurate image.
Not alpha or beta because they could damge the paper
Properties of waves
Waves transfer energy in regular oscillations through a medium. They don't transfer mass (particles)
Frequency is the amount of waves that pass a point in one second. Measured in Hertz (Hz).
Two types of waves: Longitudinal waves and Transverse waves.
Longitudinal - particles oscillate in the direction of travel.
Transverse - particles oscillate at right angles to the direction of travel
Compression - point on a longitudinal wave where the particles are closest together.
Rarefaction - Point on a longitudinal wave where particles are furthest apart
Amplitude - Point of Maximum displacement from the undisturbed position.
Wavelength - the distance between a point on the wave to the corresponding point on the next
Period - The time needed for one wave to pass a given point
Wave speed = frequency * wavelength
Reflect - the wave bounces off the boundary
Specular - Reflection off a smooth surface. Light rays reflect and travel in the same direction, leaving a clear reflection.
Diffuse - Reflection off a rough surface. Light rays scatter in different directions
The wave changes direction and speed when entering the new medium. From a high to low density - wave speeds up and refracts away from the normal line. Wavelength increases. Low to higher density - wave slows down and refracts towards the normal line.Wavelength decreases
The wave travels through the new medium
Longitudinal seismic waves. Travel faster than S-waves so are felt first. can be transmitted through liquids, so are refracted through the outer core.
Transverse seismic waves. More violent than P-waves and cause more damage. Travel slower so are felt a couple of minutes after initial P-waves. Can only be transmitted through solids so can't travel through the outer core, leaving a large shadow zone in the opposite hemisphere of where it started.
Light filters transmit the wavelength of light that the filter is.
A primary colour filter (eg. red) would block every wavelength of visible light excecpt for (red).
A secondary colour filter (eg. magenta) would block every wavelength except for the two wavelengths that coulour is made of (blue and red)
Coloured objects absorb other wavelengths of light, and reflect the wavelength that is their colour into our eyes so they appear that colour. This happens under white light because it is made up of all wavelengths of visible light, reflecting the correct one; absorbing all the others
Measuring Wave Speed
1) Measure the distance to a building. 2) Fire a starting pistol and start a timer. 3) Stop the timer when an echo is heard. 4)Half your value for time. 5) Work out the speed using s =d/t equation
Range of human hearing - 20Hz - 20kHz
Ultrasound - sound with a higher wavelength than what humans can hear. >20kHz
Black body radiation
Perfect black body - absorbs all infrared radiation it comes into contact with. Emits all IR it has.