electromagnetic waves

1、7.11Electromagnetic waves1 the features of electromagnetic waves3 The electromagnetic spectrum4 The types of electromagnetic waves2 where electromagnetic waves come fromThe features of electromagnetic waves(1 )they can travel through a vacuum (2 )With a speed of 300 000kilometres per second,(3)Trans

2、verse waves. Oscillations of electric and magnetic fields are at right-angles to the direction of travel. (4)They transfer energy called the speed of light, but it is the speed for all electromagnetic waves. Transverse wavesThe structure of atom NucleusProton NeutronsInside the condensed nucleusElec

3、tronsMoving around the nucleusSources of waves- oscillation of charged particlesThe hot, glowing bulb filamentsThe atoms osicllate or lose energy, emitting infrared, visible or ultraviolet light.The greater the energy change, the shorter the wavelength of light. Sources of waves- oscillation of curr

4、ent(a) oscillation of current(b) The change of current with timeThe higher the frequency of oscillation, the shorter the wavelength of light.The electromagnetic spectrumRadio wavesOscillation of a current in a transmitting aerial (antenna)Radio using the long and medium wavesThe microphone using VHF

5、UHF and microwave used for TV broadcastsMicrowave used for mobile phoneInfrared radiation The motion of atoms and molecules. Its radiation is a wide range of wavelengths.Infrared photo of planeInfrared photo of red-crowned cranesUltraviolet radiationSterilizing equipment to kill bacteria (germs)Fluo

6、rescence excited by ultraviolet radiationOn the other, ultraviolet is harmful to living cells of body Infrared and ultraviolet light in spectrumA beam of white light from very hot filamentInfrared radiationultraviolet radiationX-rays and Gamma raysX-rays are given off when fast-moving electrons lose energy very quickly.the treatment of cancerGamma or X-ray-type photograph