Waves we can’t see…

EM Spectrum The electromagnetic spectrum is the entire range of EM waves. It is divided into regions according to the length of the waves. All EM waves travel at the same speed in a vacuum – but the wavelength and frequency differ

EM Spectrum The EM spectrum goes from low frequency/high wavelength to high frequency/low wavelength

Radio Waves Have the longest wavelength/lowest frequency of all EM waves Any EM wave that has a wavelength of longer than 30 cm is classified as a wavelength. Radio stations encode sound information into radio waves by varying the waves’ amplitude or frequency – this change is called modulation. (AM or FM radio stations)

AM vs. FM AM – longer wavelengths than FM Can bounce off the atmosphere Can travel farther FM – less affected by electrical noise – so sounds transferred are clearer and sound better

TV Television signals are also carried by radio waves. Most use shorter wavelengths and higher frequencies than radio stations TV stations use FM waves to carry sound and AM waves to carry pictures

Microwaves Shorter wavelengths and higher frequencies than radio waves Wavelength between 1 mm and 30 cm. Cell phones use microwaves Signals sent between Earth and satellites use microwaves. Radar also uses microwaves (Radio Detection and ranging) – used to detect speed of objects.

Infrared Waves Shorter wavelengths and higher frequencies than microwaves. Wavelengths are between 700 nanometers and 1 mm. (nanometer is m) Suns rays are infrared – this is what heats your body. The waves cause the particles in your skin to vibrate more, creating heat. Almost all objects give off infrared waves Not visible to naked eye, but there are infrared cameras that will detect them

Visible Light A very narrow range of wavelengths and frequencies that humans can see Wavelengths between 400 nm and 700 nm Some energy from the sun is visible light – called white light. White light is a combination of all visible light wavelengths

Colors Humans see the different wavelengths of visible light as different colors. Longest wavelength is red – shortest is violet This range of colors is called the visible spectrum ROY G BIV

Ultraviolet Light Wavelengths vary between 60nm and 400 nm Bad effects on humans – UV light causes sunburns, skin cancer, wrinkles, and damage to eyes Good effects on humans – UV waves kill bacteria on food and other objects. Cause skin cells to produce vitamin D which allows the intestines to absorb calcium Most UV light waves are blocked from reaching Earth by the Earth’s atmosphere.

X-Rays Wavelengths between.001 nm and 60 nm. Because they are so small, they can pass through many materials, including human soft tissue. X-Ray machines used for security and medical

Gamma Rays Shortest wavelengths – shorter than.1nm Can penetrate most materials very easily Used to treat some forms of cancer Also used to kill bacteria in foods