Year 10 Students,

This is our wiki where we will compose projects, notes and information on our Physics topics. I will start it with an essay on the EM Spectrum with deliberate errors.... See if you can spot them and correct them!


The Electromagnetic Spectrum

The electromagnetic spectrum is a family of waves that are caused by disturbances in electromagnetic fields. These waves are transverse which means that the disturbance that caused the wave is in the same direction as the wave travels. There are 6 members of the EM spectrum. They are, in order of decreasing frequency and decreasing wave lengths - this can't be right as we know that as frequency increases, wavelength decreases. Can anyone correct this?? MsOD: gamma rays, x-rays, ultraviolet rays, visible light, infra red radiation, microwaves and radio waves.

The energy of electromagnetic radiation is linked to its frequency, a theory first discovered by Max Planck and used by Albert Einstein to win a Nobel Prize for his explanation of the photoelectric effect. Frequency and energy are linked by the equation E=hf. This means that the energy of an EM wave is inversely proportional to its frequency.

The different waves in the electromagnetic spectrum have different uses. The lower frequency waves are mainly used for communication (radio- and micro-waves) while the higher frequency waves are more penetrating and can be used to see inside the human body.

It may seem that mobile phones cause negligible radiation in comparison to microwave ovens but a simple calculation will show you the opposite. If you talk on the cellular phone just one hour a day the whole radiation is as follows: 1 hr a day x 365 days a year = 365 hours 365 hours x 3 watts = 1095 watts 1095 watts x 10 years = 10950 watts!!! I see a hole in your logic - the Watt is the Joule/second. You need to calculate the amount of energy. You would then need to think about whether all this energy is transferred into your body or not. Once you've found out what percentage of the energy is absorbed, you can go ahead and calculate how much energy is absorbed per year.

10.000 watts radiation of cellular phone (ten times more powerful than microwaves ovens) is as if you would put your head in a microwaves oven. You can imagine what would happen to you... you would burn like a sausage.

Cell phone can do biological damage through heating effects >>>> This causes: headaches, earaches, blurring of vision, short-term memory loss, numbing, tingling, and burning sensations, bad sleep. Do you have a source for this information? If so, please state it so we can all have a look at it and check your information - are you a scientist???

Decide for yourself!

Advantages and Disadvantages of Different Telescopes - Please add your thoughts/notes below - remember to add your sources to make your information credible and give some indication of who you are. MsOD

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