P2 - Revision Summary

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Electromagnetic waves transfer energy as photons.

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As the frequency of an EM radiation increases the amount of energy carried by each photon increases.

The intensity of a beam of EM radiation means how much energy arrives at each square metre of surface per second. It is measured in W/m^2.

3 types of ionising radiation are UV, X-rays and gamma rays.

Ionising radiation is dangerous if it occurs in your cells because it can damage your DNA causing mutations and very high does can kill your cells altogether.

Radiographers protect themselves from x-rays by wearing lead aprons or by standing behind concrete to protect themselves from x-rays.

Infrared radiation is used in conventional cookers.

Microwaves cook food as they make water particles vibrate,heating them up. The higher the power rating of a microwave the higher the intensity of the radiation and the less time it takes to cook your food.

3 greenhouse gases are: co2, methane and water vapour.

Ozone is made when UV radiation splits an ordinary o2 atom into two oxygen atoms, one of these combines with another o2 molecule to form an ozone molecule o3.

Co2 is returned to the atmosphere in the carbon cycle through respiration in plants and animals & respiration from the decomposition of plants and animals. Also from burning trees or coal.

Over the last 150 years the level of co2 in our atmosphere has been rising.

The effects of chopping down and burning trees adds co2 to the atmosphere as plants are the main thing which removes co2 - fewer trees means less co2 is taken out and burning trees adds lots of co2 into the atmosphere.

Global warming is a type of climate change which causes an increase in the overall temperature.

There is a link between the concentration of co2 and the global temperature.A lot of evidence shows the rise in co2 level is causing global warming by increasing the greenhouse effect.

Consequences of global warming are sea level rising as the sea gets warmer,ice melting and more extreme weather.

Radio waves are good at transmitting information over long distances as they do not get absorbed by the earth's atmosphere as much as other EM waves.

Microwaves are used for mobile phone and satellite communication.

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Noise has less effect on digital signals and can be cleaned up easily, they are higher quality, you can transmit several signals at once using just one cable and they are easy to process on computers.