How Do X-Rays Work
By: Carrie Lisle
Discovery of the X-ray
• Original inventor- A. W. Goodspeed on February
22, 1890
• Had no information or proof, didn’t take credit
• November 8, 1895, discovered by Wilhelm
Conrad Roentgen
Discovery of the X-ray
• Discovered by accident
• Wilhelm was experimenting
with electron beams in a
glass discharge tube
• Fluorescent screen in lab glowed when electric
beam was turned on
• Tube was surrounded by heavy black cardboard
which should have blocked radiation
Discovery of the X-ray
• Tried putting various
objects between tube and
screen
• Put hand in front of tube,
saw silhouette of bones
• Called “X” rays because it
was an unknown type of
radiation
• Name stuck despite friends’ suggestion
for “Roentgen” rays
What is an X-ray?
• Similar to visible light rays
• Both are wavelike forms of
electromagnetic energy carried
photons
• Have different energy levels
• Eyes aren’t sensitive to higher energy level
and shorter wavelengths of x-rays
• Both produced by movement of electrons in
atoms
What is an X-ray?
• Electrons occupy different orbitals
• Electrons dropping to another orbital releases
energy in the form of electrons in atoms
• Photon energy level depends on how far the
electron is dropped
• Photon-atom collisions may cause atoms to
absorb energy
• Photons’ energy level must match the difference
between the orbitals
What is an X-ray?
• Atoms making up body tissue absorb visible
light photons very well
• X-rays have too much energy,
and therefore pass through
most things
• Soft body tissue doesn’t
absorb X-ray photons well
• Calcium atoms in bones
absorb X-ray photons well
The Light
Spectrum
G
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X
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U
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AV
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O
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V
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S
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B
L L
E I
G
H
T
I
N
F
R
A
R
E
D
M
I
C
R
O
W
A
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The X-ray Machine
• Machine passes
current through
filament, heating
it up
• Heat sputters electrons
off filament surface
• Anode draws electrons
across tube
The X-ray Machine
• Electrons fly through
tube with high force
• Electron and tungsten
atom collide
• Knocks one of atoms
electrons loose
• Another electron
takes empty place
• Releases extra
energy in photon
form- high energy
The X-ray Machine
• Atom’s nucleus can
attract a speeding
electron enough to
change it’s course
• Approaching nucleus,
electron slows down
and changes direction
as it passes the atom
• Slowing down causes electron to emit excess
energy in X-ray photon form
The X-ray Machine
• High-impact collisions
generate a lot of heat
• Rotating motor keeps
anode from melting
• Entire mechanism is
surrounded by a thick
lead shield
• Shield keeps X-rays from
escaping in all directions
The X-ray Machine
• A small window in the
shield lets out the
photons in a narrow
beam
• Beam passes through
filters on way to patient
• Camera on opposite side of patient records
X-ray pattern
• X-ray cameras see chemical reactions, not
visible light
The Harm of X-rays
• X-rays hit an atom, knocking
off electrons to create an ion
• Ions cause unnatural
chemical reactions inside
cells
• Charge can break DNA chains
• Cells with broken strands of DNA will die or
develop a mutation
• Can cause various diseases or even cancer
X-ray
Radiation
• Only large amounts of
X-rays cause radiation
• Can reduce cell division
and damage genetic
material
• X-ray machine users
use protection
• Lead shields and vests
What are X-rays used for?
• Used in radiation treatment
• To look at bones
• To see possibly swallowed
things in the body
• To see gunshot wounds
• To look at gallstones
• To examine teeth
• In crystal research
Bibliography
• Dugdale, David. “How X-rays Work.” February
2004. 29 April 2004. <http://www.keele.ac.uk/depts/
uso/hs/rad/xrays.html>
• Jacikas, Kelly and Mark Woodland. “X-Rays.” 16
October 2002. 29 April 2004.<http://www.sanjuan.
edu/schools/arcade/XrayWJ.html>
• Juhl, Katie. “How do X-rays Work.” 26 April 2004.
<http://www.cord.edu/faculty/manning/
physics215/studentpages/katiejuhl.html>
•Moncton, David E. “X-Rays.” World Book. 2003 ed.
About the
Author
Hi! My name is Carrie
Lisle. I chose to do xrays for my project
because I’ve always
wondered how
doctors could see to
your bones and
security at the airport
could see what was in
people’s bags.