ems Flashcards
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List the EM waves in increasing wavelength with rough values
- Gamma ray (< 10^-11 m)
- X-ray (< 10^-8m)
- Ultraviolet radiation (< 700nm / 7 * 10^-7 m)
- Visible light (700nm <= x <= 400nm)
- Infra-red radiation (< 10^-3 m)
- Microwave (< 1m)
- Radiowave (1m <= x)
note: wavelength of visible light usually expressed in nm
List >=5 properties of EM waves and highlight which properties are unique to them
- Tranverse waves
- Comprise of electric and magnetic fields oscillating at 90° to each other
- Transfer energy from one place to another
- They can travel through a vacuum and do not require a medium to travel from one point to another
- They travel at a speed of 3.0 x 10^8 m/s in vacuum
- They obey the equation v = f(lambda)
- They obey the laws of reflection and refraction
- They carry no electric charge
- Only their speed and wavelengths change from one medium to another and not frequency since frequency depends only on the source of the wave
Waves with (?) pentrate the atmosphere with a smaller loss of energy
higher frequency / shorter wavelength
State the uses of radio waves
- Radio and television communication
- RFID tags
- Satellite televisions and internet
Why are radio waves with higher frequencies used for transfer of information?
They can carry more information per unit time
State the uses of microwaves
- Mobile phones
- Microwave oven
- Satellite television
Explain how microwaves of 2450Hz in ovens heat up water/food
allows water molecules with natural frequency of 2450Hz to resonate with it, gain kinetic energy, and hence increase in temperature
State the uses of IR radiation
- IR remote controllers
- Intruder alarms
- Thermal imaging
- Reponsible for heating of Earth by Sun
State the uses of visible light
- Photography
- Optical fibres in medicine and telecommunication
- Fog an ordinary photographic film
State the uses of UV radiation
- Sunbeds
- Bank note authentication
- Disinfecting water
- Sterilise medical equipment
State the uses of X-rays
- Radiology
- Defect detection
State the uses of gamma rays
- Kill cancerous cells
- Sterilisation of medical equipment
State the hazards for each of the EM waves
- Radio / Microwaves: slight heating when absorbed by body.
- IR radiation: cause burns
- visible light: high power (e.g. lasers) can damage eyes
- UV radiation: change structure of skin’s DNA and cause skin cancer
- X-ray / Gamma ray: ionising radiation can damage biological molecules and cells to lead to abnormal patterns of cell division, potentially causing cancer
State 2 properties of X-rays that allow it to detect broken bones
- Can penetrate matter such as tissues but not dense matter like bones
- Cause reactions on photographic films that turn exposed parts black
Explain how X-rays photograph bones + produce an image of broken bones
X-rays pass through flesh but not to the same extent through bones.
X-rays are detected photographically on a film behind the bones on which a pattern of varying depths of blackness will be produced
Dense objects such as bones display brighter because they block more of the X-ray and reduce the film’s exposure
On the contrary, air and breaks in the bones display darker due to higher film exposure.
State what is ionisation
removal of electrons from atoms/molecules to form ions
