Transcript Electromagnetic Spectrum

• An electromagnetic wave is a wave that
consists of electric and magnetic fields
that vibrate at right angles to each
other.
• An electric field surrounds every
charged object. You see the effect of
electric fields whenever you see
objects stuck together by static
electricity.
• A magnetic field surrounds every
magnet. Because of magnetic fields,
paper clips and iron filings are pulled
toward magnets.
• Electromagnetic radiation is energy
that travels in waves and in all
directions in space.
• The entire range of EM waves is called
the electromagnetic spectrum. The
electromagnetic spectrum is divided
into regions according to the length of
the waves.
• Radio waves have the longest
wavelengths (>30 cm) and the lowest
frequencies of all EM waves.
• Radio waves are used for broadcasting
radio signals.
• Microwaves have shorter wavelengths
(1mm – 30 cm) and higher frequencies
than radio waves.
• Microwaves are used to send
information over long distances.
• Cellular phones send and receive
signals using microwaves.
• Signals sent between Earth and
artificial satellites in space are also
carried by microwaves.
• Microwaves are used in radar. Radar
(RAdio Detection And Ranging) is used
to detect the speed and location of
objects.
• Radar sends out microwaves that
reflect off an object and return to the
transmitter. The reflected waves are
used to calculate speed.
• Infrared waves have shorter
wavelengths (700 nanometers (nm) and
1 mm) and higher frequencies than
microwaves.
• Visible light is the very narrow range of
wavelengths (400 – 700 nm) and
frequencies in the EM spectrum that
humans eyes respond to.
• Humans see different wavelengths of
visible light as different colors. The
longest wave-lengths are seen as red
light. The shortest wave-lengths are
seen as violet light.
• Ultraviolet waves have shorter
wavelengths (60 – 400 nm) and higher
frequencies than visible light.
• Too much UV light can cause sunburn.
UV light can also cause skin cancer and
wrinkles, and damage the eyes.
• Ultraviolet waves produced by UV lamps
are used to kill bacteria on food and
surgical tools. Small amounts of UV light
are beneficial to your body, causing skin
cells to produce vitamin D.
• X Rays have wavelengths between 0.001 nm
and 60 nm. X rays can pass through many
materials, making them useful in the medical
field.
• However, too much exposure to X rays can
damage or kill living cells.
• Gamma Rays have wavelengths shorter
than 0.1 nm. They can penetrate most
materials easily.
• Gammas rays are used to treat some
forms of cancer. Doctors focus the rays
on tumors inside the body to kill the
cancer cells.
• Gamma rays are also used to kill
harmful bacteria in foods, such as meat
and fresh fruits.