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)
Gamma ray
Emitted by nuclei
Detected by photographic film, geiger-muller tubes
Used for treating cancer
Detecting faults in metals and concrete
Sterilising equipment or killing bacteria in food
Can damage or mutate human cells, which can lead to cancer
X-ray
Emitted by atoms
Detected by photographic film
Used for x-ray photographs in medicine
Detecting faults in metals and concrete
Can damage human cells
Electromagnetic hazards
Overexposure to certain types of electromagnetic radiation can be harmful
Higher the frequency of the radiation, the more damage it is likely to cause to the body
Microwaves can cause internal heating of body tissues
Infrared radiation is felt as heat and cause skin to burn
X-rays damage cells causing mutation and cell death. May lead to cancer
Gamma rays also damage cells causing mutation and cell death