revision unit 8

Question 1

what are electromagnetic waves

Answer 1

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

Question 2

what is the speed of travel of all electromagnetic waves

Answer 2

300 million m/s

Question 3

what is white light

Answer 3

it is the ordinary light from lamps and sunlight and it contains all the colours in the spectrum from red to violet

Question 4

explain what happens to light in film camera

Answer 4

the light is focused by the lenses of the camera onto the light-sensitive film

Question 5

explain what happens to light in digital camera

Answer 5

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

Question 6

what does all object emit

Answer 6

all object emit infrared radiation the hotter the object is.

Question 7

what can infrared radiation be used in

Answer 7

1. optical fibers since infrared is absorbed less
2. remote controls
3. infrared scanners that detect the hotspots in the body
4. infrared camera which provides night vision, to see people and animals in the dark

Question 8

what are the uses of microwaves

Answer 8

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

Question 9

how do we use radio waves to communicate

Answer 9

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

Question 10

what is altering voltages

Answer 10

the are an electrical signal that constantly changes direction

Question 11

the shorter the wavelength

Answer 11

1. the more information they carry
2. the shorter there range
3. the less they spread-out

Question 12

what are the uses of radio waves

Answer 12

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

Question 13

explain how radio singles would transfer when you phone a friend

Answer 13

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

Question 14

what are optical fibers

Answer 14

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

Question 15

what is the difference between optical fibers and radio and micro waves communications

Answer 15

1. optical fibers carry much more information, because the light was smaller wavelength compared to radio waves
2. optical fibers are more secure as they don’t leave the the fibers

Question 16

is mobile radiation dangerous

Answer 16

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

Question 17

how is ultraviolet radiation harmful to humans

Answer 17

1. it damages the eyes and can cause blindness

2. to much of ultraviolet waves can cause sun burn and potentially skin cancer

Question 18

how are x-rays and gamma rays similar

Answer 18

1. they are at the short-wavelength end of the electromagnetic spectrum
2. carry much more energy that the rest of the electromagnetic waves

Question 19

how are x-rays and gamma rays different

Answer 19

1. x-rays are made at a x-ray tube where fast moving particles or electrons are stopped
2. gamma rays are produced by radioactive substances when unstable nuclide release energy
3. gamma rays penetrate more than x-rays

Question 20

what are the use of gamma radiation

Answer 20

1. killing harmful Bactria in food
2. sterilizing surgical instruments
3. killing cancer cells

Question 21

what is the process of ionizations

Answer 21

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

Question 22

why do you make radiograph

Answer 22

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

Question 23

how can x-rays treat cancer

Answer 23

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.

Question 24

explain how CT scanners work

Answer 24

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

Question 25

the detector signal depend on

Answer 25

1. the amount of tissues in the x-ray paths

2. how far can the x-ray penetrate each tissue

Question 26

what is the difference between the ordinary x-ray machine and the CT scanner

Answer 26

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