Spectra
● Dispersion of light
○ The phenomenon of splitting up of a white light into its constituent colours
○ E.g. rainbow
● The cause of dispersion of light is that white light consists of 7 different colours
● Electromagnetic waves can all be reflected, refracted and diffracted
● Wavelength decreases ------->
● Frequency increases --------->
● Energy increases -------->
Uses of electromagnetic waves
● Radio waves
○ Detected by aerials
○ Used for communication (broadcast radio and television signals)
● Microwaves
○ Detected by aerials (diodes)
○ Communication (satellite television broadcasting)
○ Cooking
○ Used to transmit mobile phone signals between masts
● Infrared
○ Emitted by hot objects
○ Detected by skin/ thermometer/ photographic film
○ Used for seeing
● Ultraviolet radiation
○ Emitted by hot objects
○ Detected by skin, photographic film
○ Used for sun tanning
○ Energy efficient lamps
○ Phototherapy
○ Killing bacteria (water disinfection)
○ Creating fluorescent effects
○ Equipment disinfection (food, beverage, air)