Physical Science 9
Unit 5: The Power of the Nucleus
Activity #4: Exposure to Radiation
#4
To Begin
Radiation is energy that “radiates” (spreads out) from its source. Electromagnetic radiation is a form
of energy emitted by charged particles. Most notably, the high-energy particles in the Sun emit a large
amount of electromagnetic radiation. A campfire also emits electromagnetic radiation. Many different
human technologies are purposefully designed to emit electromagnetic radiation. Nuclear radiation
originates in the nucleus of an atom. Some elements have naturally occurring radioactive (unstable)
isotopes. A well known example is the element uranium, which has several radioactive isotopes. Many
different human technologies have been developed using nuclear radiation, including smoke detectors and
nuclear energy.
Learning Goals
Students will be able to…
 Compare and contrast electromagnetic radiation with nuclear radiation.
 Interpret a diagram of the electromagnetic spectrum and use it to explain differences in radiation
energy.
 Understand how ionizing radiation is more dangerous for humans than non-ionizing radiation.
Electromagnetic Radiation Spectrum
A spectrum refers to a range of variation. In the Electromagnetic Radiation Spectrum, the spectrum has
to do with the energy of the radiation, from highest energy at one end to lowest energy at the other end.
Imagine you are a holding a jump rope with a friend, and you begin to move the rope so that it has up and
downs waves, only slowly and with little energy. Later, you move it much faster to make high energy
waves. In the space below draw the rope showing these two different types of wave behavior.
Slow,
low energy
Fast,
high energy
Which of your drawings shows a wave with a longer wavelength? (low or high energy)_______________
Electromagnetic radiation is transferred across space. Think of how far the electromagnetic radiation
emitted from the Sun travels until it reaches Earth. This radiation is delivered by photon particles that
exhibit wave-like behavior. High- energy radiation consists of higher frequency, shorter wavelengths.
Low-energy radiation consists of lower frequency, longer wavelengths.
There are many types of electromagnetic radiation. The particular type depends on the amount of energy
in the radiation. On the next page, you will complete a diagram that illustrates the full spectrum of
electromagnetic radiation. Follow the instructions a – d (you will complete “e” at a later time).
ELECTROMAGNETIC RADIATION SPECTRUM
a. Wavelength:
(Draw one long repeating wave that changes wavelength as you move along the spectrum)
b. Complete the expanded visible light spectrum
c. Frequency :
(draw an arrow in the direction of low to high)
d. Amount of energy:
(draw an arrow in the direction of low to high)
e. Mark/ label on your diagram where non-ionizing radiation ends and ionizing radiation begins.
Physical Science 9
Unit 5: The Power of the Nucleus
Activity #4: Exposure to Radiation Reader
#4
CLASS COPY
READ COLLABORATIVELY!
Nuclear Radiation
Nuclear radiation originates in the nucleus of the atom. The nucleus contains protons and neutrons that
are held together, and kept stable, by an extremely strong force. (This strong force has been named
“strong force”!). When something disrupts the stability of an atom, the nucleus will emit the excess
energy as radiation. There are four types of radiation that can be emitted from an atomic nucleus: alpha
particle radiation, beta particle radiation, gamma and x-radiation, and neutron particle radiation.
Alpha particles are charged particles emitted from naturally occurring materials (uranium and radium)
and man-made elements (plutonium and americium). These alpha emissions are primarily used (in very
small amounts) in items such as smoke detectors.
Beta particles are similar to electrons and are emitted from naturally occurring materials such as the
radioactive isotope of carbon. Such beta emitters are used in medical applications, such as treating eye
disease.
Gamma rays and x-rays consist
of high-energy waves that can
travel great distances at the speed
of light. Gamma rays are often
used in medical applications to
treat cancer and sterilize medical
instruments. X-rays are typically
used to provide images of body
parts (such as teeth and bones), and
are also used in industry.
Fig. 1.
Figure 1 compares the different forms of nuclear radiation and their various abilities to penetrate material.
As you can see alpha particles are stopped by paper or skin. Smoke detectors emit alpha particle radiation
which is not able to penetrate your skin. Beta particles can penetrate skin but can be stopped by a thin
sheet of plastic or wood. X-rays and gamma rays can only be stopped by dense material (such as lead) or
by several feet of concrete (like a thick concrete wall).
**Based on this information, use reasoning to assess which type of nuclear radiation has the most energy
and which type has the least energy. DISCUSS THIS WITH YOUR GROUP!
Neutrons are the fourth form of nuclear radiation. This radiation is the highest-speed, highest-energy
nuclear radiation. Because of their exceptional ability to penetrate other materials, neutrons can travel
great distances in air and require very thick hydrogen-containing materials (such as concrete or water) to
block them. Fortunately, however, neutron radiation primarily occurs inside a nuclear reactor, where
many feet of water act as a shield to provide effective protection.
Ionizing Radiation vs Non-Ionizing Radiation
Ionizing radiation has enough energy to cause atoms to ionize. As you
learned in Chapter 4, ionization is the process in which an electron is
given enough energy to break away from the atom. This process results
in the formation of two charged particles: the ion with a net positive
charge, and the free electron with a negative charge. All ionizing
radiation is capable, directly or indirectly, of removing electrons from
atoms.
Fig. 2
Figure 2 is a diagram showing incoming ionizing radiation. The diagram shows the energy from the
radiation is transferred to the electron which breaks away from the atom.
Both particles, the positive ion and the free electron, are highly reactive. They are capable of reacting
with other atoms and molecules to cause chemical changes in the cells of living tissue. These types of
changes can result in damage to a cell or tissue. Fortunately, most living tissue have effective repair
mechanisms that are in constant operation.
All types of nuclear radiation are ionizing. Only some forms of electromagnetic radiation are ionizing
(some UV, x-rays and gamma rays).
**COMPLETE “e” on your Electromagnetic Radiation Spectrum diagram.
Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy
to result in an ionization of an atom. In other words, low to medium energy (low-medium frequency
wavelength) electromagnetic radiation will not remove an electron from an atom.
As non-ionizing radiation passes through matter, the
electromagnetic radiation has sufficient energy only for electron
excitation. As you learned in Chapter 4 (the flame test), electron
excitation is the absorption of energy by an electron so that it
has enough energy to “jump” to a higher energy level within the
atom.
Some ultraviolet, visible light, infrared, microwave, and radio waves are all examples of non-ionizing
radiation. These types of radiations can increase the vibrations of atoms, increase the kinetic energy of
the atoms. The increase in kinetic energy causes an increase in the temperature of the matter. This is how
microwave ovens are able to heat up our food.
The light from the Sun that reaches the earth is largely composed of non-ionizing radiation, with the
notable exception of some ultraviolet rays. However, most ionizing electromagnetic radiation (some UV
radiation, x-rays and gamma rays) is filtered out by the Earth's atmosphere.
** Why is it important that we shield ourselves from x-rays? Why do we not bother protecting ourselves
from microwave radiation or visible light radiation? DISCUSS THIS WITH YOUR GROUP!