is10_sb_unit_d

Electromagnetic radiation is a wave pattern made of electric and
magnetic fields that can travel through empty space. The entire range of
electromagnetic radiation extends from the shortest gamma rays to the
longest radio waves and includes light. This range is called the
electromagnetic spectrum (Figure 10.8 ).
3
infrared waves
4 Ultraviolet rays carry more energy
than visible light and therefore have a
shorter wavelength and higher
frequency than visible light. The main
sources of ultraviolet radiation are the
Sun and other stars. A small amount of
ultraviolet radiation is beneficial to
human health. However, extended
exposure to ultraviolet radiation can
burn the skin and increase the risk of
skin cancer.
Ultraviolet radiation is used to
disinfect drinking water and waste water
and in DNA analysis (Figure 10.12). It is
also used in detective work to reveal the
presence of substances that cannot be
seen under visible light.
Figure 10.12 Scientists analyzing
DNA over an ultraviolet light box need
to wear a shield to protect their eyes
from the UV light.
visible light
4
ultraviolet rays
5
X-rays
gamma rays
5 X-rays are very high energy
6 Gamma rays are extremely high
radiation that can penetrate human energy radiation that can penetrate
tissues. X-rays have difficulty passing human tissues. Gamma rays are used
through bone, making them useful for to sterilize medical equipment. Doctors
medical imaging. X-rays are also used use short bursts of gamma rays from
as a security measure to scan luggage different angles in order to kill a
at airports. The rays pass through the maximum number of cancerous cells
clothes in the luggage but are absorbed and a minimum number of healthy
by metal or hard plastic objects.
cells. Technicians who work with high
Another use for X-rays is photographing energy waves such as X-rays and
the inside of engines, pipelines, and gamma rays must wear a shield, such
other machines to check for fractures or as a lead apron, to protect themselves
damage (Figure 10.13).
from radiation. Gamma rays are
produced within our galaxy and in other
galaxies by phenomena such as
neutron stars and black holes
(Figure 10.14).
Figure 10.13 A photograph of the inside
of binoculars taken with X-rays
Suggested Activity •
D4 Quick Lab on page 390
Light is part of the electromagnetic spectrum and travels in waves.
6
Figure 10.14 A map of the universe
made using gamma rays
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