A1 Conceptual Physics
Spring 2011
Quantum and Nuclear
Chapters 31, 38 and 39
Conceptual Physics Quantum Outline
Hewitt: Chapter 31, 38, 39
Exercises: 18 Modern Physics
Formula Chart*
Energy of photon
de Broglie
Wavelength
Photoelectric Effect
hf = KE + Φ
Activity
Half Life
Fill in the Charts completely
Variables introduced or used in chapter:
Quantity
Symbol Units
Energy
Planck’s Constant
Frequency
Photon Energy
Work Function
Φ
J
Kinetic Energy
decay constant
Half life
Define the following terms using COMPLETE SENTENCES:
Chapter 31:
Chapter 38:
Coherent:
Photoelectric effect
Diffraction:
Photon
Diffraction Grating
Planck’s constant
Hologram
Quanta (singular:
Huygens’s principle
quantum)
Incoherent:
Quantum mechanics
Iridescence:
Quantum physics
Laser
deBroglie Wavelength
Monochromatic
Chapter 39
Atomic mass number
Atomic number
Half – life
Isotope
Nucleon
Radioactive
Strong force
Weak force
Quantum
Formulas:
hf = KE + Φ
E=hf
KE = ½ mv2
h =λp = λmv
mproton = 1.67x10-27 kg melectron = 9.1x10-31kg c = 3.0 x 108 m/s
h= 6.63 x 10-34 Js=4.14 x 10-15eVs
1eV = 1.60 x 10-19 J
UV:
c = fλ
1nm = 10-9m
below 400 nm
Yellow light 530 – 590 nm
Violet light 400 – 440 nm
Orange light 590 – 630 nm
Blue light
Red light
440 – 480 nm
Green light 480 – 530 nm
76
630 – 700 nm
Infrared radiation:
above 700 nm
A1 Conceptual Physics
Spring 2011
Quantum and Nuclear
Chapters 31, 38 and 39
Homework Problems
Conversions / Energy conversion
c = 3.0 x 108 m/s
1nm = 10-9m
1. Convert to nanometers (nm)
a. 789 x 10-7 m [78900 nm]
b. 789 x 10-8 m [7890 nm]
c. 789 x 10-9 m [789 nm]
d. 789 x 10-10 m [78.9 nm]
e. 789 x 10-11 m [7.89 nm]
f. 789 x 10-12 m [0.789 nm]
2. Convert to meters (m)
a. 0.125 nm [1.25 x 10-10m]
b. 1.25 nm [1.25 x 10-9 m]
c. 12.5 nm [1.25 x 10-8 m]
d. 125 nm [1.25 x 10-7 m]
3. Calculate the amount of energy released when 2.3 kg of uranium 235 is
converted to energy in a fission reaction. [2.07 x 1017 J]
4. Calculate the amount of energy released when 15 kg of plutonium is converted
to energy in a fission bomb. [1.35 x 1020J]
5. A nuclear bomb releases
of energy. Calculate the mass of the bomb
that was converted to energy. [7.0 x 10-4 kg, 0.7 g]
6. Ms Jensen loses the specs for her diffraction grating and must recalibrate in
order to determine the grating spacing. She shines a red helium-neon laser,
with a wavelength of 633 nm through the grating. Two bright spots which are
1.40 m from the central maximum fall on the wall that is 4.00 m away. What is
the space between the groves on the diffraction grating?[1.81 x 10-6 m, 1810
nm]
7. Using the same diffraction grating, Ms Jensen tries to determine the wavelength
of a green helium-neon laser. Keeping the laser at the same distance from the
wall (4.00m) the distance from the central maximum to the first bright fringe is
1.20 m. What is the wavelength of the HeNe laser? [543 nm]
8. Judy and Earl are sitting under the boardwalk one warm summer evening while
the light of a low-pressure sodium vapor lamp whose wavelength is 589 nm
passes through two small cracks in a board, producing fringes of light 0.0020 m
apart on the ground.
a. If the board walk is 3.0 above the sand, what is the distance between the
two cracks in the board? [8.8 x 10-4m]
b. If the distance between the cracks were smaller, would the fringes of
light on the ground be closer or father apart? [farther]
9. Two loudspeakers broadcast the sound of a band tuning up before an outdoor
concert. While the band plays an A whose wavelength is 0.733m, Brenda walks
to the refreshment stand along a line parallel to the speakers. If the speakers
are separated by 12.0 m and Brenda is 24.0 m away, how far must she walk
between the ‘loud spots’? [1.46m]
10. In an attempt to test the particle nature of matter, Claus Jonsson performed an
experiment in 1961 that was very similar to Young’s Double slit experiment for
light that was done in 1801. Jonsson sent a beam of electrons through two slits
separated by 2.00 x 10-6 m onto a fluorescent screen 0.200 m away. Due to
77
A1 Conceptual Physics
Quantum and Nuclear
Spring 2011
Chapters 31, 38 and 39
their high speed, the electrons behaved like waves with a wavelength of 2.40 x
10-11m. How far apart were the bright lines formed on the screen? [2.4x10-6m]
11. Jon puts on a pair of diffraction gratings glasses that he bought at a novelty
shop and looks at a mercury vapor street lamp that is 5.00 m away. He sees a
yellow spectral line 1.16m on either side of the light source. If the diffraction
grating glasses have a slit separation of 2.49 x 10-6 m, what is the wavelength
Jon is looking at? [578 nm]
12. Houston radio station KKRW 93.7 has two transmitters that sit atop nearby
buildings broadcasting a wave that is 214 m long. As Kiesha drives down I-10
parallel to the two transmitters at a distance of 100.0m, she hears an increase
in signal form the station every 30.0 m. How far apart are the two
transmitters? [713.3 m]
De Broglie Waves
E=hf
h =λp = λmv
h= 6.63 x 10-34 Js
1eV = 1.60 x 10-19 J
13. Glenn is a DJ at his high school radio station PHYS, which broadcasts at a
frequency of 91.7 MHz. When the station is on the air, how much energy does
each emitted photon possess?
a. In Joules? [6.08 x 10-26 J]
b. In electron volts? [3.8 x 10-7 eV]
14. Bart uses a helium-neon laser to align his telescope. The laser emits red light
with a wavelength o f633 nm. How much energy, in electron volts, is given off
by each photon of laser light? [3.14 x 10-19J, 1.96 eV]
15. Compare the de Broglie wavelengths for a proton and an electron, each
traveling at 3.00 x 107 m/s.
[p: 1.32 x 10-14m, e: 2.43x 10-11m]
16. The sun is a yellow star and emits most of its radiation in the yellow portion of
the spectrum. If the sun’s radiation peak at a frequency of 5.20 x 1014Hz, how
much energy is emitted by one photon of this visible light? [3.45x10-19J, 2.15eV]
17. After applying sunscreen, Cherie lies in the sun to get a tan. The ultraviolet
light responsible for tanning has a wavelength of 310 nm, while the burning
rays can range down to 280 nm.
a. Calculate the energy of the tanning rays [6.42 x 10-19 J, 4.01 eV]
b. Calculate the energy of the burning rays [7.10 x 10-19 J, 4.44 eV]
c. Which is has more energy, by how much? [burning, 0.43 eV]
18. Gayle cooks a roast in her microwave oven. The klyston tube in the oven emits
photos whose energy is 1.20 eV. What are the wavelengths of these photos?
[1035 nm]
19. During the winter Olympic biathlon trials, Eric is shooting his rifle at a target.
What is the de Broglie wavelength of a 10.0 g bullet firing form the rifle at 500
m/s? [1.33 x 10-34 m]
20. An Electron microscope is observing detail on a virus down to 5.0 nm. How fast
must an electron in the microscope be moving to observe detail this size (HINT:
Due to diffraction, the electron’s wavelength must be about the same size or
smaller than the object observed) [150,000 m/s]
78
A1 Conceptual Physics
Spring 2011
PHOTOELECTRC EFFECT
E=hf
h =λp = λmv c = fλ
-34
h= 6.63 x 10 Js 1eV = 1.60 x 10-19 J
Quantum and Nuclear
Chapters 31, 38 and 39
hf = KE + Φ
21. When Doug walks through the entrance to the hardware store, a bell in the back
of the store rings, triggered by a photocell whose work function is 2.40 eV.
a. What is the threshold frequency of the light shining on the photocell?
[5.797 x 1014 Hz]
b. What is the wavelength of light? [518 nm]
c. What color is this? [blue]
22. What is the kinetic energy of photoelectrons emitted when UV light of 200 nm
shines on a photocell whose work function is 2.50 eV? [5.95 x 10-19J]
23. The work function for three surfaces are: Wmercury = 4.5 eV, Wmagnesium = 3.85 eV,
Wlithium = 2.30 eV.
a. At what threshold frequency are electrons liberated from each of these
surfaces? [1.09 x 1015Hz, 9.30 x 1014 Hz, 5.55 x 1014 Hz)
b. What color light is corresponds to each? [275 nm – UV, 338 nm – UV,
541 nm - Yellow]
24. Shelby shines a red, helium-neon laser, with a wavelength of 633 nm, on a
photo cell that has a work function of 2.38 eV.
a. Will the photocell function with this wavelength? [no]
b. What wavelength corresponds to the threshold frequency? [522 nm]
25. A classic physics demonstration involves placing a shiny zinc plate on a
negatively charged electroscope and shining UV light on the plate. If the work
function of zinc is 4.31 eV and the wavelength of light is 250 nm,
a. What is the kinetic energy of the photoelectrons ejected from the zinc
plate? [0.66 eV]
b. What will happen to the leaves of the electroscope? [They will close]
Energy Level Diagrams
26. What wavelengths of light are emitted by an electron jumping from n=2 to
n=1? What does it correspond to? [122 nm, UV]
27. What wavelengths of light are emitted by an electron jumping from n = 4 to n =
3? [1880 nm, Infrared]
28. Using the energy level diagram, determine the shortest wavelength in diagram
for level three to infinity of hydrogen [832 nm]
29. The sun’s spectrum is made up of many absorption lies called Fraunhofer lines
( α line). How many electron volts of energy are absorbed in order to produce
the H α line whose wavelength is 657.7 nm? [1.89 eV]
30. A stellar spectrum shows three absorption lines of hydrogen produced as
electrons move from n=2 to higher energy levels (n=3, n=4, n=5) What are the
wavelengths and colors of the three lines missing from the continuous
spectrum? [657 nm, Red; 488 nm, Greenish blue; 435 nm, Violet]
31. On June 24, 1999, NASA launched FUSE (the Far Ultraviolet Spectroscopic
Explorer) to explore the universe using high- resolution spectroscopy in the far
UV spectral region. If FUSE records radiation of wavelength 102.8 nm:
a. What is the energy required to make the jump? [12.09 ev]
79
A1 Conceptual Physics
Quantum and Nuclear
Spring 2011
Chapters 31, 38 and 39
b. between which two energy levels mist the electron jump in the
hydrogen atom to produce this line? [n=3 and n=1]
Half Life/Radiation
32. Cobalt-60, used in radiation therapy for cancer patients has a half-life of 5.26
yr. A sample of cobalt 60 containing 5.00 x 1012 radioactive atoms sits in a lead
case in the medical stockroom of Ben-Taub for 10.0 years.
a. What is the decay constant for cobalt-60? [0.132 / yr]
b. How many cobalt – 60 atoms remain? [1.33 x 1012 atoms]
33. Radioactive gold-198 is used as a tracer in liver tests in low level scans. Dr. R
uses gold-198 in a scan on Patient X who has been exhibiting signs of jaundice.
A solution containing 3.00 x 109 gold – 198 atoms is injected into his live and
observed after 70.0 hr.
a. What is the decay constant of the gold if the half life is 2.70 days?
[0.0107 / hr]
b. How many gold atoms are remaining after 72.0 hours? [1.39 x 109
atoms]
c. What is the activity of the gold-198 in Bq? [-4130 Bq]
34. Spent fuel rods contain strontium-90 whose half life is 28.1 yr. Josh works at a
nuclear reactor and must safely store the spent rods. If a spent rod contains 1.0
x 1027 atoms of strontium-90 when stored in a sealed container, how many
strontium-90 atoms will remain if the container is excavated by archeologists in
1000 years? [1.85 x 1016 atoms]
35. The synthetically manufactured radiopharmaceutical technicium-99 is used to
produce brain scans. The half life of technicium-99 is 6.02 hr. What percent of
technicium-99 remains 24 hours after the scan? [6.3 %]
80
A1 Conceptual Physics
Spring 2011
Quantum and Nuclear
Chapters 31, 38 and 39
RADIOACTIVE HALF LIFE Lab
PROBLEM:
Radioactive isotopes decay at different times. How to you determine
the half-life of radioactive materials when given the change in mass over a
period of time?
MATERIALS: 100 small disks or pennies, shoebox or other box with lid, timer, graph
paper
PROCEDURE & OBSERVATIONS:
1. Each group of students will get a box with 100 disks or pennies to start.
2. Make sure that each disk has a spot on one side and clear on the other side. For
pennies, use heads and tails.
3. Shake the box and spill out the contents. Remove any disks with the spot or the
heads of pennies. Count how many disks or pennies were left after the removal.
4. Put the disks or pennies that were not removed back into the box and shake the
box again. Spill out the contents and remove the disks with spots or the pennies
with the heads side up. Count how many are left and put the ones that have not
been removed back into the box.
5. Repeat the procedure until all pennies or disks have been removed. Record Trial
and number left for each trial.
6. On the graph, plot the number of disks or pennies left in the game after each toss
by placing the toss number on the horizontal axis and the number of disks or
pennies left after each toss on the vertical axis
7. Draw a smooth curve that passes close to the points on the plot.
QUESTIONS:
1.
Compare your graph to the graph on page 615 of your Conceptual Physics
textbook. How is your graph’s curve similar to the graph in your textbook?
2.
If a sample of radioactive isotope has a half-life of 1 year, how much of the
original sample will be left at the end of the:
A. second year?
B. third year? C. fourth year?
3.
When an atom undergoes radioactive decay, does it become a completely
different element? Explain.
4.
Why did it take so long to remove all of the pennies (disks)? Do you think
that it will always take the same amount of time to remove all of the
pennies (disks) if you did the experiment again? (Check with other teams to
compare your results.)
CONCLUSION: Write a Conclusion about half-life. Did this lab work?
Rubric:
Data Chart : 20 pts
Questions: 4 x 5 pts = 20 pts
81
Graph: 40 pts
Conclusion: 20 pts
A1 Conceptual Physics
Spring 2011
Quantum and Nuclear
Chapters 31, 38 and 39
Review Sheet:
Chapter references are in parenthesis at end of each question.
1. Why is blue light used to view tiny objects in an optical microscope? (31.2)
2. Why is it important that monochromatic light (single frequency) be used in
Young’s interference experiment? (31.4)
3. If the double slits were illuminated with monochromatic blue light, would the
fringes be closer together or farther apart than those produced when
monochromatic red light is used? (31.4)
4. What color will reflect from a soap bubble in sunlight when its thickness is such
that red light is canceled? (31.6)
5. The left column lists some colored objects. Match them to the various ways that
light may be produce that color from the choices in the right column. (31.6)
a. Yellow banana
1. Interference
b. Blue sky
2.Diffraction
c. Rainbow
3. Selective reflection
d. Peacock feather
4. Refraction
e. Soap bubble
5. Scattering
6. What is Huygens Principle? (31.1)
7. Waves spread out when they pass through an opening. (31.1-31.2)
a. Does the spreading become more or less pronounced as the opening
narrows?
b. What is this spreading out called?
8. Does diffraction aid or hinder radio reception? (31.2)
9. Does diffraction aid or hinder the viewing of images in a microscope? Why?
(31.2)
10. Can waves cancel each other? Why or why not?
11. Does wave interference occur for all waves or only light? What is an example?
(31.3 – 31.4)
12. What was Thomas Young’s discovery? (31.4)
13. What is the causes of fringes of light in Young’s experiment? (31.4)
14. What is a diffraction grating? (31.4)
15. What is required for a part of the light reflected from a surface to be canceled
by another part reflected by the surface? (31.5)
16. What causes the bright and dark fringes visible in lenses that rest on flat plates
of glass? (31.5)
17. What is iridescence?(31.6)
18. What causes iridescence? (31.6)
19. If a soap bubble is thick enough to cancel yellow light by interference, what
color will it appear to be in white light? (31.6)
20. Why is gasoline that is spilled on a wet surface so colorful? (31.6)
21. What is an interferometer? (31.6)
22. What physics principle is an interferometer based? (31.6)
23. What does LASAR mean? (31.6)
24. How does laser light differ from light from a regular lamp? (31.7)
25. Will brighter light eject more electrons from a photosensitive surface than a
dimmer light of the same frequency? (38.3)
26. Will high-frequency light eject a greater number of electrons than lowfrequency light? (38.3)
27. What fundamental force dictates the size of an atom? (38.7)
82
A1 Conceptual Physics
Quantum and Nuclear
Spring 2011
Chapters 31, 38 and 39
28. Give two examples of a model for explaining light (38.1)
29. What is a quantum? Give 2 examples (38.2)
30. What is a quantum of light called? ( 38.2)What is Planck’s constant and how
does it relate to the frequency and energy of a quantum light? (38.2)
31. Which has more energy per photon – red light or blue light? (38.2)
32. What is the photoelectric effect? (38.3)
33. Why does blue light eject electrons from a certain photosensitive surface,
where red light would have no effect? (38.3)
34. Will bright blue light eject more electrons than dim light of the same light of the
same frequency? (38.3)
35. Does the photoelectric effect support the particle or wave theory of light? (38.3)
36. Do particles of matter have wave properties? (38.5)
a. What is the name of the physicist who gave the first convincing
argument?
37. As the speed of a particle increases, does the wavelength increase or decrease?
( 38.5)
38. Does the diffraction of an electron beam support the wave or particle model of
electron? (38.5)
39. How does the energy of a photon compare with the difference in energy levels
of the atom from which it is emitted? (38.6)
40. What does it mean to say that an electron occupies discrete energy levels in an
atom? (38.6)
41. Does the particle view of an electron or the wave view of an electron better
explain the discreteness of electron energy levels? Why? (38.6)
42. What does wave interference have to do with the electron energy levels in an
atom? (38.6)
43. Why is a helium atom smaller than a hydrogen atom? (38.7)
44. Why are the heaviest elements not larger than the lighter elements on the same
row? (38.7)
45. What is quantum mechanics? (38.8)
46. Can the momenta and positions of electrons be measured with certainty? (38.8)
47. Pretend you are given three radioactive cookies: 1 alpha, one beta and one
gamma. Pretend you must eat one, hold one and put the other in your pocket.
Which would you eat, hold and pocket to minimize your exposure to radiation?
[39.3]
48. If a sample of radioactive material has a half life of 1 year, how much of the
original sample would be left after 2 years? (39.5)
49. If you have equal amounts of radioactive materials, one that has a short half life
and another that has a long half life – which will give the higher reading on a
radiation detector? (39.5)
83