Download Understanding Electromagnetic Waves: Radio to Gamma Rays and more Study notes Geography in PDF only on Docsity! Wavelength and Energy relationship – Everyday experience Radio Waves: I like these waves; they are used for radio broadcasts, amateur radio, television, and mobile phones. Different parts of the radio spectrum have been allocated to the various services. Radio waves have a much longer wavelength that light waves. The longest waves are several kilometers in length. The shortest ones are only millimeters long. The really nice thing about radio waves is that they will make the electrons in a piece of copper wire move; this means that they generate electric currents in the wire. In fact it works both ways: alternating currents in a copper wire generate electromagnetic waves, and electromagnetic waves generate alternating currents. The electric currents at "radio frequencies" (rf) are used by radio and television transmitters and receivers. I use frequencies of 145MHz (VHF), 14MHz (20m HF) and 3.7MHz (80m HF). Microwaves: Microwaves have such a short wavelength that they are very easily absorbed by water. This is why they are used in microwave ovens. What happens is that when the water in your TV dinner absorbs the microwaves, the energy of the microwaves is converted into heat: it makes the water molecules vibrate faster. Some people are frightened that the radio waves coming out of their mobile phones are short enough to cook their brains. Infra Red: These radio/light waves have a very short wavelength; their wavelength is longer than visible light. Infra-red can be detected by special infra-red film. If the police or MI5 shine an infra-red light on you they will be able to take a picture of you using infra-red film: you will not know that they have taken your photo. You have been warned!!! Animals like the pit-viper have infra-red detectors so that they can find their prey in the dark. You have been warned again!!! The Visible Spectrum: Richard Of York Gave Battle In Vain. = Red, Orange, Yellow, Green, Blue, Indigo, and Violet. are the colours of the visible spectrum. We cannot see Infra-red, but we can feel it warm our skin when we sit in the sun. Infra-red has a longer wavelength (less energy) than Red light. We cannot see Ultra-violet light, but we feel our skin has been burnt by the sun if we were in the sun too long yesterday. It is the Ultra- violet which is thought to cause skin cancer. UV light has a shorter wavelength (more energy) than visible light. Ultra Violet: These waves have very high energy and very short wave lengths; shorter than visible light. Some animals like honey bees can see ultra-violet light. Some plants have white
