Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
|
Order the electromagnetic spectrum from highest to lowest wavelength.
|
Radio, microwaves, infrared, light, ultraviolet, X-rays and gamma radiation.
This is also the lowest to highest energy. |
|
|
What speed to electromagnetic waves travel?
|
300 million m/s or 300000 km/s.
|
|
|
What devices use infrared?
|
Optical fibres use infrared radiation since infrared is absorbed less than visible light in the glass fibres.
Remote control handsets. Infrared scanners are used in medicine to detect hot spots on the body surface. Infrared cameras can see people and animals in darkness. |
|
|
What do we use microwaves for?
|
Communication, like satellite TV, since they can pass through the atmosphere to reach satellites. We also use them to beam signals from place to another since they spread out less than radio waves. Microwaves and radio waves carry mobile phone signals.
|
|
|
What do we use radio waves for?
|
They can carry radio, TV, and mobile phone signals. They can also connect a computer to other devices wirelessly.
|
|
|
Why is infrared radiation dangerous?
|
It can heat up skin cells and damage or kill them.
|
|
|
Why are microwaves and radio waves dangerous?
|
They can penetrate our bodies and heat the internal parts of our bodies.
|
|
|
What does decreasing the wavelength of radio waves and microwaves do?
|
They can carry more information.
They have a shorter range (due to increasing absorption by the atmosphere). The less they spread out (because they diffract less). |
|
|
Compare optical fibres with radio waves and microwaves.
|
Optical fibres carry much more information and are more secure because the signals stay in the fibre.
|
|
|
Why is ultraviolet radiation dangerous?
|
It is harmful to the human eye and can cause blindness. It can cause sunburn and skin cancer.
|
|
|
How are X-rays and gamma rays different?
|
X-rays are produced when electrons or other particles moving at high speeds are stopped. X-ray tubes are used to produce X-rays.
Gamma rays are produced by radioactive substances when unstable nuclei release energy. Gamma rays have shorter wavelengths than X-rays and can penetrate more substances than X-rays. |
|
|
What are the uses of gamma radiation?
|
Killing harmful bacteria in food.
Sterilising surgical instruments. Killing cancer cells. |
|
|
Why are X-rays and gamma rays dangerous?
|
They can knock electrons out of atoms, ionising them. Ionisation is dangerous since it can kill living cells or cause cell mutation and cancerous growth.
|
|
|
What safety measures are taken when working with X-radiation and gamma radiation.
|
Wearing a film badge tells you how much ionising radiation you have received, you aren't allowed to work for a period of time if the badge says you are over-exposed.
|
|
|
How do you make a radiograph?
|
A lightproof cassette containing photographic film or a flat-panel detector is placed on the other side of the patient while X-rays from an X-ray tube are directed at the patient.
X-rays pass through soft tissues but are absorbed by bones so the bones appear lighter than the surrounding area. An organ consisting of soft tissue must be filled with a contrast medium which absorbs X-rays easily, allowing its internal surfaces to be seen. Lead 'absorber' plates between the tube and the patient stop X-rays reaching other parts of the body. A flat-panel detector is a small screen that contains a CCD. The sensors in the CCD are covered by a layer of a substance that converts X-rays to light, which is then sent to a computer, displaying the X-ray image. |
|
|
How does a CT scanner work?
|
An X-ray tube automatically moves around the inside of the ring in small steps, and emits X-rays at every position. Electronic signals from the detector are recorded by a computer which then displays a digital image of the scanned area.
|
|
|
Compare a CT scanner with an ordinary X-ray machine.
|
CT scanners can distinguish between different types of soft tissues.
CT scanners give a 3D image. CT scanners are more expensive and give a much higher dose of radiation. |
