P13 Better Flashcards
What are electromagnetic waves
Transverse waves that transfer energy from the source of the waves to an absorber
How do all electromagnetic waves travel
They all travel at the same velocity through a vacuum
What are the groups of electromagnetic waves in order from the shortest to the largest wavelength
Gamma rays, x-rays, ultraviolet, visible light ( violet to red ), infrared, microwaves, radiowaves
What are the electromagnetic waves in order from shortest to largest frequency
radio, microwave, infrared, visible light (red to violet), ultraviolet, X- rays and gamma rays
What electromagnetic waves do our eyes detect
Our eyes only detect visible light and so detect a limited range of electromagnetic waves
How do different substances interact with electromagnetic waves and what does this depend on
Different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength.
Some effects, for example refraction, are due to the difference in velocity of the waves in different substances
How are radio waves produced
Radio waves can be produced by oscillations in electrical circuits.
What may happen when radiowaves are absorbed
When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit
How do atomic changes interact with electromagnetic waves
Changes in atoms and the nuclei of atoms can result in electromagnetic waves being generated or absorbed over a wide frequency range. Gamma rays originate from changes in the nucleus of an atom
Which electromagnetic waves can have bad effects on humans
Ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue
What do the negative effects from electromagnetic waves depend on
The effects depend on the type of radiation and the size of the dose
What is radiation dose and what is it measured in
Radiation dose (in sieverts) is a measure of the risk of harm resulting from an exposure of the body to the radiation
How do millisieverts compare to sieverts
1000 millisieverts (mSv) = 1 sievert (Sv)
What are the risks of ultraviolet, gamma and x-rays
Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer.
X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer.
What are the practical uses of the EM spectrum
- radio waves – television and radio
- microwaves – satellite communications, cooking food
- infrared – electrical heaters, cooking food, infrared cameras
- visible light – fibre optic communications
- ultraviolet – energy efficient lamps, sun tanning
- X-rays and gamma rays – medical imaging and treatments
