Download Science 8: Unit C: Light and Optical Systems

Science 8: Unit C: Light
and Optical Systems
Topic 8: Beyond Light
The Invisible Spectrum
• Stars and galaxies which
produce light radiation also
produce a wide spectrum of
waves which are invisible to our
eyes. Everything from radio
waves with 1-2 km in
wavelength to high energy
gamma rays.
Electromagnetic
Radiation (EMR)
• Is radiation produced by a
vibrating electric and magnetic
fields.
• The entire family of EMR is
called the electromagnetic
spectrum (EMS)
• All EMR behaves as a wave:
they travel at the speed of light,
reflect, refract, diffract, absorb,
etc.
Radio Waves
• Have the longest wavelength
and lowest frequency of the
EMS. They are used for AM and
FM radio signals and TV signals.
• Radio waves are going through
us all the time, but because
they are such low energy they
are not considered a health
hazard.
Microwaves
• A form of higher energy radio
radiation.
• Microwaves are used to vibrate
water particles in food, heating
them up.
• They are also used in satellite
and cellphone technology.
Infrared Radiation
• Heat radiation. Has a longer
wavelength than red light.
• Anything that is above absolute
zero emits infrared radiation,
including you.
• TV remotes, heat lamps, and
burglar alarms.
Snake held by a human
hand as seen through
infrared radiation.
Ozone Layer
• The following EMR
are too short to
pass through the
ozone layer
because they’re
wavelength is too
small. Even blue
and purple light
rays are scattered
by the ozone layer,
making the sky
blue.
Ultraviolet Radiation
• Just past the purple range of light
lies UV radiation.
• Most UV radiation produced by the
sun is reflected by the Ozone layer in
the atmosphere.
• This is a good thing because UV
radiation has a high enough
frequency and energy to penetrate
and mutate skin cells, tanning our
skin, burning our skin, and if given
enough exposure, causing skin
cancer.
X-Rays
• Shorter wavelength and higher
energy than UV. X-rays can
penetrate and mutate skin and
soft tissue, but not bone.
• X-rays are used by doctors and
dentists, however, they’re no
longer used to try on shoes.
Gamma Rays
• The shortest wavelength gamma
rays and therefore highest energy.
• They can penetrate, mutate, or kill
all tissue including bone, making
them very dangerous.
• Because of their ability to kill cells
gamma rays are used to try and kill
cancer cells. This is called radiation
therapy. The downside to this
therapy is that you often kill healthy
surrounding cells as well as the
tumor.
The Gamma Ray Sky