# 10.7 Medical applications and biological effects of nuclear radiation  (Page 3/18)

 Page 3 / 18
1. Retreat to an irreversible state of dormancy (known as senescence);
2. Commit suicide (known as programmed cell death); or
3. Progress into unregulated cell division, possibly leading to tumors and cancers.

Nuclear radiation can harm the human body is many other ways as well. For example, high doses of nuclear radiation can cause burns and even hair loss.

Biological effects of nuclear radiation are expressed by many different physical quantities and in many different units. A common unit to express the biological effects of nuclear radiation is the rad or radiation dose unit . One rad is equal to 1/100 of a joule of nuclear energy deposited per kilogram of tissue, written:

$1\phantom{\rule{0.2em}{0ex}}\text{rad}=0.01\phantom{\rule{0.2em}{0ex}}\text{J}\text{/}\text{kg}.$

For example, if a 50.0-kg person is exposed to nuclear radiation over her entire body and she absorbs 1.00 J, then her whole-body radiation dose is

$\left(1.00\phantom{\rule{0.2em}{0ex}}\text{J}\right)\text{/}\left(50.0\phantom{\rule{0.2em}{0ex}}\text{kg}\right)=0.0200\phantom{\rule{0.2em}{0ex}}\text{J}\text{/}\text{kg}=2.00\phantom{\rule{0.2em}{0ex}}\text{rad}.$

Nuclear radiation damages cells by ionizing atoms in the cells as they pass through the cells ( [link] ). The effects of ionizing radiation depend on the dose in rads, but also on the type of radiation (alpha, beta, gamma, or X-ray) and the type of tissue. For example, if the range of the radiation is small, as it is for $\alpha$ rays, then the ionization and the damage created is more concentrated and harder for the organism to repair. To account for such affects, we define the relative biological effectiveness (RBE). Sample RBE values for several types of ionizing nuclear radiation are given in [link] .

Relative biological effectiveness
Type and Energy of Radiation RBE [1]
X-rays 1
$\gamma$ rays 1
$\beta$ rays greater than 32 keV 1
$\beta$ rays less than 32 keV 1.7
Neutrons, thermal to slow (<20 keV) 2–5
Neutrons, fast (1–10 MeV) 10 (body), 32 (eyes)
Protons (1–10 MeV) 10 (body), 32 (eyes)
$\alpha$ rays from radioactive decay 10–20
Heavy ions from accelerators 10–20

A dose unit more closely related to effects in biological tissue is called the roentgen equivalent man (rem)    and is defined to be the dose (in rads) multiplied by the relative biological effectiveness (RBE). Thus, if a person had a whole-body dose of 2.00 rad of $\gamma$ radiation, the dose in rem would be $\left(2.00\phantom{\rule{0.2em}{0ex}}\text{rad}\right)\left(1\right)=2.00$ rem for the whole body. If the person had a whole-body dose of 2.00 rad of $\alpha$ radiation, then the dose in rem would be $\left(2.00\phantom{\rule{0.2em}{0ex}}\text{rad}\right)\left(20\right)=40.0$ rem for the whole body. The $\alpha$ rays would have 20 times the effect on the person than the $\gamma$ rays for the same deposited energy. The SI equivalent of the rem, and the more standard term, is the sievert (Sv)    is

$1\phantom{\rule{0.2em}{0ex}}\text{Sv}=100\phantom{\rule{0.2em}{0ex}}\text{rem}.$

The RBEs given in [link] are approximate but reflect an understanding of nuclear radiation and its interaction with living tissue. For example, neutrons are known to cause more damage than $\gamma$ rays, although both are neutral and have large ranges, due to secondary radiation. Any dose less than 100 mSv (10 rem) is called a low dose    , 0.1 Sv to 1 Sv (10 to 100 rem) is called a moderate dose    , and anything greater than 1 Sv (100 rem) is called a high dose    . It is difficult to determine if a person has been exposed to less than 10 mSv.

A round diaphragm S with diameter of d = 0.05 is used as light source in Michelson interferometer shown on the picture. The diaphragm is illuminated by parallel beam of monochromatic light with wavelength of λ = 0.6 μm. The distances are A B = 30, A C = 10 . The interference picture is in the form of concentric circles and is observed on the screen placed in the focal plane of the lens. Estimate the number of interference rings m observed near the main diffractive maximum.
A Pb wire wound in a tight solenoid of diameter of 4.0 mm is cooled to a temperature of 5.0 K. The wire is connected in series with a 50-Ωresistor and a variable source of emf. As the emf is increased, what value does it have when the superconductivity of the wire is destroyed?
how does colour appear in thin films
in the wave equation y=Asin(kx-wt+¢) what does k and w stand for.
derivation of lateral shieft
hi
Imran
total binding energy of ionic crystal at equilibrium is
How does, ray of light coming form focus, behaves in concave mirror after refraction?
Sushant
What is motion
Anything which changes itself with respect to time or surrounding
Sushant
good
Chemist
and what's time? is time everywhere same
Chemist
No
Sushant
how can u say that
Chemist
do u know about black hole
Chemist
Not so more
Sushant
DHEERAJ
Sushant
But ask anything changes itself with respect to time or surrounding A Not any harmful radiation
DHEERAJ
explain cavendish experiment to determine the value of gravitational concept.
Cavendish Experiment to Measure Gravitational Constant. ... This experiment used a torsion balance device to attract lead balls together, measuring the torque on a wire and equating it to the gravitational force between the balls. Then by a complex derivation, the value of G was determined.
Triio
For the question about the scuba instructor's head above the pool, how did you arrive at this answer? What is the process?
as a free falling object increases speed what is happening to the acceleration
of course g is constant
Alwielland
acceleration also inc
Usman
which paper will be subjective and which one objective
jay
normal distributiin of errors report
Dennis
normal distribution of errors
Dennis
acceleration also increases
Jay
there are two correct answers depending on whether air resistance is considered. none of those answers have acceleration increasing.
Michael
Acceleration is the change in velocity over time, hence it's the derivative of the velocity with respect to time. So this case would depend on the velocity. More specifically the change in velocity in the system.
Big
photo electrons doesn't emmit when electrons are free to move on surface of metal why?
What would be the minimum work function of a metal have to be for visible light(400-700)nm to ejected photoelectrons?
give any fix value to wave length
Rafi
40 cm into change mm
40cm=40.0×10^-2m =400.0×10^-3m =400mm. that cap(^) I have used above is to the power.
Prema
i.e. 10to the power -2 in the first line and 10 to the power -3 in the the second line.
Prema
there is mistake in my first msg correction is 40cm=40.0×10^-2m =400.0×10^-3m =400mm. sorry for the mistake friends.
Prema
40cm=40.0×10^-2m =400.0×10^-3m =400mm.
Prema
this msg is out of mistake. sorry friends​.
Prema
what is physics?