Edexcel P1 Topic 2

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  • Created by: Hannah
  • Created on: 20-05-12 10:35

Herschel dounf infrared radiation when experimenting with sunlight and a prism. When white light goes through a prism, it creates a spectrum of colours. He used this equipment to make a spectrum of the screen. He wante to know the amount of heat in each of these colours. He used a thermometers to measure each colour temperature in turn. He noticed they increased for violet to red. He then measured the temperature past the red part of the spectrum where they're was no visble light. He found here had the highest temperature of all, he had discovered infrared radiaton and invisble type of radiation

Ritter wanted to see wether he could find anything on the other side of the spectrum. He conducted the same equipment as Herschel but apart from using sunlight. He used a light source. He wantd to measure how quickly silver chloride coated strips changed when exposed to different colours of the spectrum since sliber chlorides turns from white to balck when exposed to light. He timed how long it took the strips of light to turn black and he noticed the strips changed the quickest when exposed to light near the blue end of the spectrum. He then placed a strip pass the violet part of the spectrum, here he saw the quickest change of all. he had discovered ultraviolent radiation, an invisble form of light exsists in the oher side of the spectrum.

All EM waves are transverse wave and travel at the same speed. This means EM waves with a higher frequency has a short wavelength. As the frequency increases, the wavelength decreases. As the frequency changes , it interaction with matter changes also, e,g, the way the wave is absorbed, reflected or transmitted by a given substance depend on it's frequency. The EM waves at the end of the spectrum tend to pass through material whilst the ones in the middle absorb. The effects of EM radiation in human depends on the frwuency as weel since frequency determines the energy of the wave. The more freuqucy, the higher the energy, the more harmful.

Microwaves have a similar frequency to the vibrations of molecules. Microwaves can heat human body cells.Mobile phones use microwavesand their is cocnerns as the hnadsets are usual held close to the brain.

Infrared has a range of frequencies which causes surface molecules of any substances to vibrate which causes a heating effect but they have a higher frequency they contain more energy so if the human body is exposed to too much infrared radiation it can cause skin burn.

Ultraviolent has more energy because it has a higher energy. It is ionising so it carries enough energy to know electrons off atoms. Sunburn happens when surface skin cells have been damaged by absorbing UV rays in sunlight. This causes cell mutation or destruction and skin cancer. UV rays in sunlight causes eye damge.

Gamma or X rays has a very high frequency and are ionising so it carres more energy than UV…

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