Like sound waves and waves in water,
light waves can travel through matter.
Light waves can travel through space
that contains almost no matter.
• Electromagnetic waves are waves that can
travel through matter and through empty
space. Light travels fastest through empty
space and slowest through solids.
Wavelength of light
• Wavelength of light are usually measured in a
unit called the nanometer (nm).
• 1 m= 1,000,000,000 nm
Properties of Light Waves
• Light waves and all electromagnetic waves are
• An electromagnetic wave has an electric part
and a magnetic part. Both are called fields.
• The frequency of an electromagnetic wave is
the number of times the electric and magnetic
fields vibrate in one second.
• The wavelength of an electromagnetic wave is
the distance between the crests or troughs of
the vibrating electric or magnetic parts.
Intensity of Light
• The intensity of wave is a measure the amount
of energy that the waves carry. The intensity
of light waves tell how bright a light is. A dim
light has lower intensity. Its waves carry less
energy. A bright light has higher intensity. Its
waves carry more energy.
• There are many kinds of electromagnetic
• The electromagnetic spectrum is made of all
the frequencies and wavelengths of
• At one end of the spectrum are the waves that
have the lowest frequency. They also have the
lowest energy and the longest wavelength. At
the other end of the spectrum are waves that
have the highest frequency. They also have
the highest energy and the shortest
• Radio waves have the lowest frequency on the
electromagnetic spectrum. They are on the
left side of the electromagnetic spectrum.
They carry television and radio signals into
your home. These waves have the longest
• The shortest radio waves are called
microwaves. Microwaves are used to cook
food in microwave ovens. They also carry
information to and from cell pones.
• You use infrared waves when you use a
remote control to change the channel on your
television. Infrared waves carry information
from the remote control to the television.
• There are special night goggles that pick up
infrared waves. They can be used to see
people in the dark.
• There is part of the electromagnetic spectrum
that people can see called visible light.
• The color of the light you see depends on the
wavelength of the light waves. Violet light has
the shortest wavelength. Red light has the
• The light from the Sun or from a flashlight is
white light. White light is a combination of
different colors. You see this as a rainbow of
colors coming out of the prism.
• Ultraviolet waves are shorter and carry more
energy than visible light waves.
• There are ultraviolet waves in sunlight. Some
exposure to ultraviolet waves is good for you.
• Ultraviolet waves help your body make
vitamin D. You need vitamin D to keep your
teeth and bones healthy.
• But, ultraviolet waves can give you a sunburn
if you stay out in the sunlight too long. Too
much sunlight can damage our skin and even
cause skin cancer.
X Rays and Gamma Rays
• X rays and gamma rays have the highest
energy, highest frequency, and shortest
wavelengths of all the waves in the
• Doctors use X rays to see broken bones. X rays
have enough energy to go right your skin. But,
they cannot pass through dense objects, such
as bones. This allows X rays to produce an
image of the inside of your body.
• Gamma rays have even more energy than X
rays. Gamma rays are used on some foods to
kill bacteria that make food spoil quickly.