X-rays in space
The swift satellite (left) has a three different
types of telescopes, one of which is an x-ray
telescope. The telescope detects x-rays
coming from the sun and stars, and
from objects such as black holes. The
satellite sends x-ray pictures back to
earth. astronomers use these pictures
to discover and understand more of
the universe.Computer receives
electrical signals from
the photodiodes
and converts
them into an
image of
the case.To The early pioneers of medicine, the thought of looking through
the body of a living person would probably have seemed like magic.
But today it is routine for doctors and dentists to take pictures of their
patients’ bones and teeth with an x-ray camera. X rays are invisible waves,
like light or radio waves. They can travel through soft materials just as
light passes through glass. For example, x-rays can travel through flesh
and skin. But hard materials such as bone and metal stop x-rays, so
bone and metal show up as a shadow on an x-ray picture. x-rays have many
uses: scientists use them to probe into the molecular structure of materials
such as plastics, and engineers make x-ray scans of aircraft to find cracks
that could cause mechanical failure. in
addition, the sun, stars, and other objects
in space produce x-rays naturally.580
Baggage scanner
airports have x-ray scanners (left)
to check baggage for weapons and
other dangerous objects. an x-ray
tube produces a beam of x-rays, and
a conveyor belt carries each suitcase
into the path of the beam. electronic
detectors pick up the x-rays once
they have passed through the case.
a computer uses signals from the
detectors to build up a picture of
the contents of the case.X-ray TuBe
like a light bulb, an x-ray
tube is filled with an inert
(nonreacting) gas, but
produces x-rays instead of light.X-ray tube
produces X rays.Conveyor
belt carries
suitcases into
the scanner.Medical x-rays
doctors and dentists use x-ray machines to
look inside their patients’ bodies without
using surgery. The machine makes an x-ray
picture using a digital sensor, or on a piece
of photographic film. The photograph is a
negative, and bones show up in white. large
doses of x-rays are harmful, so x-ray
examinations must be carefully controlled.WilhelM roenTgen
The german scientist Wilhelm roentgen
(1845-1923) discovered x-rays in 1895.
roentgen did not understand what these
rays were, so he named them x-rays.A strong electric
current heats a wire.
The energy from the
electric current knocks
some electrons out of
the atoms in the wire.A powerful electric field
pulls electrons at high speed
toward the metal target.A metal object such as a
pistol does not allow x-rays
to pass through it, so the
pistol shows up on screen.Array of photodiodes—electronic
detectors that produce electrical
signals when x-rays hit them.
Scanner is lined with
lead to prevent the
x-rays from escaping.Monitor screen displays
contents of case to
security guards.As the electrons crash into
the target, atoms of the metal
produce the x-ray beam.X-rays
Find out more
atoms and molecules
Machines
Medicine, history of
science
starsUS_580_X-rays.indd 580 27/01/16 2:41 pm