The Electromagnetic Spectrum

The Electromagnetic Spectrum

1. Visible Light

   • A prism can be used to disperse colours into a spectrum
   • The colours visible are red, orange, yellow, green, blue, indigo and violet
   • All the wavelengths are different for example red light has a longer wavelength than violet light

2. Infrared and Ultraviolet

   • William Herschel discovered infrared waves in 1800 when experimenting with a prism and sunlight
     • He found that the hottest temperatures were beyond the red end of the spectrum where there is no visible light (known as the infrared region)
     • Infrared waves have a longer wavelength than red light
   • Johann Ritter discovered Ultraviolet waves in 1801 when carrying out experiments to see if he could find anything on the other side of the spectrum beyond violet
     • UV waves have a shorter wavelength than Violet light
     • The 3 types are UV-A, UV-B and UV-C
       • UV-C causes most damage and has the shortest wavelength

3. EM Waves

   • There are 7 types of EM waves
     • Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays - decreasing wavelength and increasing frequency
   • They're all transverse waves and travel at the same speed in a vacuum (300 000 000 m/s)
   • What they do
     • Can transfer energy
     • Can be reflected, refracted and diffracted
     • Obey the wave equation
       • wave speed = wavelength x frequency