Topic Two - The Electromagnetic Spectrum Flashcards
How was infrared discovered
Infrared radiation was founded by Herschel, he put coloured filters on his telescope to observe the sun safely.
He noticed that different coloured filters heated up his telescope to different extents - he wondered whether different colours of light contained different amounts of heat;
~ to test this, Herschel used a prism to split sunlight into a spectrum and then put a thermometer in each of the colours
~ he found that as he changed the colour from violet-indigo-blue-green-yellow-orange-red, the temperature increased
Herschel then measured the temperature just beyond the red end of the spectrum, where there was no visible light, he found that this gave the highest temperature
- This band of invisible light beyond the red spectrum is called infrared radiation
Dangers of microwaves
Microwaves can heat cells inside the human body. This can damage them
Spectrum of visible light in order
Red (longest wavelength, lowest frequency) - Orange - Yellow - Green - Blue - Indigo - Violet (shortest wavelength, highest frequency)
Dangers of infrared radiation
If the human body is exposed to too much infrared radiation, it can cause some nasty skin burns
Dangers of uv radiation
This can cause skin cancer
The UV in sunlight can also cause eye damage
Dangers of x-rays and gamma rays
They can cause cell damage or cell mutation, which can lead to cancer
How was ultraviolet discovered
Ritter knew silver chloride turned from White to black when exposed to
Light
He exposed strips of silver chloride coated paper to each colour in the visible spectrum
He timed how long it took each of the strips to turn black
The strips changed quickest when exposed to light nearer the blue end of the spectrum
He placed a strip in the area just past the violet part of the spectrum - here he saw the quickest change
Ritter had discovered ultraviolet radiation
This is an invisible form of radiation just beyond the violet end of the spectrum
Use of radio waves
Television signals
Use of microwaves
Cooking, mobile phones
Use of infrared
Optical fibre communication
Use of visible light
Seeing
Use of ultraviolet radiation
Detecting forged bank notes
Uses of X-rays
Medical images of bones
Uses of gamma radiation
Killing cancer cells
Ionising radiation
Gamma rays are ionising radiation - they can remove electrons from atoms to form ions
Ions are very reactive - if atoms in the cell are ionised, the reactions that follow can damage DNA
Some elements naturally emit gamma radiation all the time - such elements are said to be radioactive
