ASSIGNMENT 10
Part One: Electromagnetic Radiation
Part One of this assignment is worth 11 marks. The value of each question is noted
in parentheses in the left margin. Note: The answer areas will expand to fit the
le
...
ASSIGNMENT 10
Part One: Electromagnetic Radiation
Part One of this assignment is worth 11 marks. The value of each question is noted
in parentheses in the left margin. Note: The answer areas will expand to fit the
length of your response.
1.
(1)
Medical technologies related to imaging and cancer treatment use high-frequency EMR.
a. Explain why high frequency EMR is harmful.
Answer: High frequency EMR is harmful due to its high energy potential. In the equation E=hf,
where E is energy, h is the Planck’s constant and f is the frequency of the EMR, the
greater the frequency, the greater its energy. When the energy of an EMR is higher, it has
a greater ionizing power, causing it to be able to penetrate stronger barriers. Most types
of EMR are easily blocked by the skin, however, EMR with higher frequencies than visible
light (ultraviolet, X-ray, gamma and cosmic radiation) are able to penetrate very strong
surfaces. Some types of EMR can cause permanent skin damage while others may
cause internal problems, radiation sickness or even death.
(1) b. What precautions should medical personnel take when working with these types
of technologies?
Answer: Medical personnel should wear protective (often lead encased) aprons and limit their
exposure to such technology. Recently, medical personnel will exit the room and use a
digital camera with robotic functions in order to take pictures that involve X-rays and other
high-frequency EMRs. This strongly lowers their exposure to high-frequency EMR.
2. A student measures the period of an electromagnetic wave as 3.64 x 10-15 s.
(1) a. What is the frequency of the wave?
Answer: T= 3.64x10-15s
T= 1/f
f=1/T
f=
1
3.64 x 10−15 s
f= 2.74725x1014 Hz
f= 2.75x1014 Hz
(1) b. What is the wavelength of the wave?
Answer: f= 2.75x1014 Hz
v= 3.00x108 m/s
Part Two: The Speed of Light
Part Two of this assignment is worth 20 marks. The value of each question is
noted in the left margin in parenthesis. Note: The answer areas will expand to fit
the length of your response.
(3) 1. If you know Earth’s orbital diameter and can measure the difference in eclipse times for
Jupiter’s moon, Io, you can calculate the speed of light. If an eclipse of Io occurred 24
min later than expected and Earth’s orbital diameter is 3.0 x 1011 m, what is the speed of
light?
Answer: t= 24 min= 1440s
d= 3.0x1011m
v=
dt
v=
3.0 x 1011m
1440 s
v= 2.1x108 m/s
(3) 2. As shown below, a rotating mirror with 16 sides was used to measure the time it took light
to travel 3.5 km to a concave mirror and back. At what frequency did the rotating mirror
need to turn such that it made 1/16th of a rotation in the time it took light to travel the 3.5
km and back again?
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