revision unit 8 Flashcards
what are electromagnetic waves
there are electric and magnetic disturbances that transfer energy that depends on the wavelength of the wave the shorter the wavelength the more energy, and they all make up electromagnetic spectrum, and they do not transfer matter
what is the speed of travel of all electromagnetic waves
300 million m/s
what is white light
it is the ordinary light from lamps and sunlight and it contains all the colours in the spectrum from red to violet
explain what happens to light in film camera
the light is focused by the lenses of the camera onto the light-sensitive film
explain what happens to light in digital camera
the light I focused by the lens on to the sensor which is made of thousands of light sensitive cells called pixels, each pixels would give a dot on the image giving the image on the screen
what does all object emit
all object emit infrared radiation the hotter the object is.
what can infrared radiation be used in
- optical fibers since infrared is absorbed less
- remote controls
- infrared scanners that detect the hotspots in the body
- infrared camera which provides night vision, to see people and animals in the dark
what are the uses of microwaves
they are used in satellite Tv as they can go outside the earth atmosphere to the the satellites above the earth, they are also used as beam signals from one place to another since they don’t diffract as much as radio waves, they are also used to carry mobile signals
how do we use radio waves to communicate
radio waves are emitted from Ariel when altering a voltage is applied, the frequency of the radio waves applied is the same as the altering voltage, so when the radio waves reaches the receiver Ariel it would cause the same altering voltage and the Ariel would be contacted to a speaker producing sound
what is altering voltages
the are an electrical signal that constantly changes direction
the shorter the wavelength
- the more information they carry
- the shorter there range
- the less they spread-out
what are the uses of radio waves
less than 1 meter wavelength - podcasting Tv
between 1 meter to 100 meter wavelength - local radio stations
more than a 100 meter - international radio stations
explain how radio singles would transfer when you phone a friend
when you phone a friend it sends out a radio signal that would be picked up by a local mobile phone mast, then the signal is send to your friends phone from the network
what are optical fibers
they are thin glass fibers, that transmit signals carried by light or infrared rays, the light cant escape the fiber once it reaches the surface it gets reflected back
what is the difference between optical fibers and radio and micro waves communications
- optical fibers carry much more information, because the light was smaller wavelength compared to radio waves
- optical fibers are more secure as they don’t leave the the fibers
is mobile radiation dangerous
mobile radiation is less powerful than microwaves in the oven, but we constantly use our phones and its close to our brain so the scientists think it might be effecting our brain but there isn’t anything certain
how is ultraviolet radiation harmful to humans
- it damages the eyes and can cause blindness
2. to much of ultraviolet waves can cause sun burn and potentially skin cancer
how are x-rays and gamma rays similar
- they are at the short-wavelength end of the electromagnetic spectrum
- carry much more energy that the rest of the electromagnetic waves
how are x-rays and gamma rays different
- x-rays are made at a x-ray tube where fast moving particles or electrons are stopped
- gamma rays are produced by radioactive substances when unstable nuclide release energy
- gamma rays penetrate more than x-rays
what are the use of gamma radiation
- killing harmful Bactria in food
- sterilizing surgical instruments
- killing cancer cells
what is the process of ionizations
when atoms become charged when they lose electrons, if ionization happens in living cells it would damage the living cell to a point where it can kill it, that’s why there is danger in exposing someone to too much radiation as it can cause cancer so people how work around radiation wear a film badge
why do you make radiograph
so x-rays from an x-ray tube is directed at the the patient with a flat-panel detector placed on the other side.
so open the x-ray tube releasing x-rays at the patient the x-rays would get absorbed by the bones and pass through the tissues so the bones would become lighter in the x-ray picture, you can also put a contrast medium in a tissue absorbing the x-ray and giving us an image of the tissue
how can x-rays treat cancer
x-rays can kill cancerous tumors, and when doctors do that they would place a lead sheet in between it and the healthy tissues to stop x-rays form reaching to it.
explain how CT scanners work
CT scanners produce a digital image of any cross-section in the body, it can also produce 3 dimensional photos of the organ, it works by a patient lieing in a bed with a ring of detectors in it, the ring would move small step and at each step it release x-rays through the patient, till it completes a full circle, the ring would be connected to computer that would take the information from the ring and present an image digitally
the detector signal depend on
- the amount of tissues in the x-ray paths
2. how far can the x-ray penetrate each tissue
what is the difference between the ordinary x-ray machine and the CT scanner
both can distinguish between bone and tissue, only CT can distinguish between different type of tissues and only CT scanners can produce a 3d image, and CT scanners are more expansive and they give a higher radiation does
