P5.2 Flashcards
What is the speed of EM waves
3 x 10^8 m/s
What is the electromagnetic spectrum in increasing wavelength?
Gamma X-rays UV Light Infrared Micro Radio
Are EM waves transverse or longitudinal?
Transverse
What em waves are used to heat up food?
Microwaves and infrared
What is the spectrum of visible light ?
The 7 colours of the rainbow, and red has the highest wavelength (approx 700nm)
How do you produce and detect radio waves?
An oscillated potential difference on a wire makes electrons move forwards and backwards
Produces a changing electric and magnetic field
Emitted as a radio wave
When it reaches another metal e.g aerial, the electrons move again producing an electrical signal
Which em waves are used for communication?
Microwaves (bluetooth)
Radio (adding sound and picture info)
Infrared (optical fibres)
Visible light (ship communication)
What em wave do dvds and cds use?
Visible light
What are some uses of UV?
Helps produce vitamin D, bodily fluids glow in UV, detecting forged bank notes
What 3 em waves can kill cells and what are the advantages and risks of these?
UV - Can sterilise water
But can damage DNA in skin causing skin cancer
Can develop cataracts in your eyes which makes corneas cloudy
X-rays - kill skin cancer and other cancer, but can also cause cancer
Gamma rays - sterilise food, kill cancer but also kill cells in your body
How are infrared waves used for imaging?
Heat produces infrared radiation,so thermal imaging cameras can detect areas of high infrared due to an injury or infection
Basically its about heat
How are X-rays used for seeing if your arm is broken?
Bones absorb x-rays but soft tissues dont,photographic film darkens upon absorbing X-rays so therefore creates an image of the inside of a person
How are X-rays used for general imaging?
A CCD can detect different intensities, densities and distances an X-ray has gone through,and computers can use X-rays to create an inside image of e.g your body, and they are used to look inside suitcases at an airport
What EM wave can be used to detect leaking pipes
Gamma rays - there will be more above leaks than the rest of the pipe (use tracers)
How are gamma rays used for imaging?
A doctor injects a patient with gamma rays.
As everything in the body transmits gamma rays,it can be used to create images of internal structures where other waves may be unable to
