Electromagnetic spectrum Flashcards
List the order of the electromagnetic spectrum from long wavelength to short wave length
Radio waves
Micro waves
Infra red
Visible light
Ultra violet light
X-ray
Gamma ray
How is the order of the electromagnetic spectrum determined
Decreasing wavelength and increasing frequency from Radio to Gamma
How is body tempertaure kept constant
It needs to radiate the same average power as it absorbs
What are radio waves used for
broadcasting, communications and satellite transmissions
What are micro waves used for
cooking, communications and satellite transmissions
What is infra red used for
cooking, thermal imaging, short range communications, optical fibres, television remote controls and security systems
What is visible light used for
vision, photography and illumination
What is ultraviolet light used for
security marking, fluorescent lamps, detecting forged bank notes and disinfecting water
What are x-rays used for
observing the internal structure of objects, airport security scanners and medical X-rays
What are gamma rays used for
sterilising food and medical equipment, and the detection of cancer and its treatment
How can micro waves be dangerous
Internal heating of body cells
How is infra red dangerous
Skin burns from an intense source
How is ultraviolet dangerous
damage to surface cells and eyes, leading to skin cancer and eye conditions
How are x-rays and gamma rays harmful
mutation or damage to cells in the body
Gamma- a big dose leads to dna breakdown-radiation sickness
X-ray- cells are altered and produce a cancerous tumour
How can radio waves be produced
Oscillations in electrical circuits
The higher the frequency of radio wave, the faster the oscillations of the electrons.
They are received by being absorbed by the electrons in a wire (eg aerial), which then start to oscillate.
Changes in an atoms nuclei can…
a) generate radiations over a wide frequency range
b) be caused by absorption of a range of radiations
How does danger increase within the EM spectrum
Danger increases with increasing frequency
What happens to the speed of the EM waves in a vacuum
The speed stays the same but their frequencies are different
What 3 groups of EM waves ionise
U-V, X-rays, Gamma rays
What is the speed at which EM waves travel through a vacuum at
3 x 10^8 m/s
Explain how radio waves can be transmitted around the curvature of the Earth
The atmosphere gets thinner as the altitude increases. Therefore radio waves refract as they rise. Unless pointed straight up, this causes them to change direction until they reach the CRITICAL ANGLE with the atmosphere (at the ionosphere), at which point they reflect back down (total internal reflection).
How is IR linked to the greenhouse gas effect
Ideally IR power absorbed by Earth = IR power radiated by Earth (earths temp stays constant)
Because the rate of IR ABSORBED is GREATER THAN the IR EMITTED, the earths surface temperature will rise until it is sufficiently hot for the rates to be equal again and stabilise at that new higher temperature
This is global warming
How and where are gamma rays produced
By an annihilation of a positron when it comes into contact with an electron - gamma rays are released
Gamma rays are produced in the nucleus
