Problems and Questions on Lecture 1 Useful equations and constants 1. 2.

Problems and Questions on Lecture 1
Useful equations and constants
1. Which of the following colors is associated with the lowest temperature of a black body radiator?
(A) Violet
(B) Blue
(C) Green
(D) Yellow
(E) Red
2. What did Max Planck propose to solve the black body radiator problem?
(A) Radiation is made up of waves.
(B) Light changes its speed in different media. (C) Light comes in packets of energy.
(D) Light has a continuous energy profile. (E) Objects do not radiate energy.
3. What is a photon?
(A) an electron in an excited state (B) a small packet of electromagnetic energy that has particle-like properties (C) one form of a
nucleon, one of the particles that makes up the nucleus (D) an electron that has been made electrically neutral
4. What is the quantization? Give examples of quantized quantities.
5. Which of the following phenomena provides the best evidence that light can have particle properties?
(A) Diffraction of light (B) Electromagnetic radiation (C) Compton effect (D) Electron diffraction (E) γ-ray diffraction
6. Which of the following photons has the greatest energy?
(A) Infrared
(B) Blue light
(C) X-ray
(D) Gamma ray
(E) Ultraviolet
7. The energy of a photon depends on its:
(A) Amplitude
(B) Speed
(C) Temperature
(D) Pressure
(E) Frequency
8. How does the energy of a photon change if the wavelength is doubled?
(A) Doubles
(B) Quadruples
(C) Stays the same
(D) Is cut to one-half
(E) Is cut to one-fourth
9. The threshold of dark-adapted (scotopic) vision is
at acentral wavelength of 500 nm. If light with this
intensity and wavelength enters the eye when the pupil is open to its maximum diameter of 8.5 mm, how many photons per
second enter the eye?
10. Calculate wavelength, momentum, and energy (eV) of a photon, having frequency 900 MHz (Cell-Phone frequency).
11. Consider a cell phone emits the power 1.0 watt (This is related to the SAR value of the cell phone machine.) How many
photons are emitted per second from the cell phone?
12. The charge on an electron is represented by “e.” Which of the following charges can exist?
(A) 2.0 e (B) 2.5 e (C) 3.6 e (D) 5.2 e (E) 5.5 e
13. How does the momentum of a photon change if the wavelength is halved?
(A) Doubles
(B) Quadruples
(C) Stays the same
(D) Is cut to one-half
(E) Is cut to one-fourth
14. Calculate momentum and energy (in eV) of the photons, having a wavelength:
a) Radio wave 3000 meter
b) Microwave 6.0 cm
c) Visible light range 600 nm
d) x-ray range 6.0 nm
e) Gamma ray 6.0 pm
15. A laser pulse of duration 25 ms has a total energy of 1.2 J. If the wavelength of this radiation is 463 nm, how many photons are
emitted in one pulse?
16. All objects of their temperature greater than absolute zero radiate energy. Why, then, are we not able see all objects in a dark
room?
17. It's commonly known that a white-painted house is a good idea in hot summer weather, because more sunlight is reflected
from the exterior, making for a cooler interior. But what of winter? Is a white-painted house a good or poor idea in cold winter
weather? Defend your answer.
18. Which is hotter, a blue flame or an orange one? Why?
19. Surface
temperature
of
sun
is
5800
K.
Using
Wien
displacement
law
(
) calculate maximum wavelength of the radiated light? (note that the maximum wavelength is in
the range of blue light.) Why isn’t the sun blue?
20. The photoelectric effect was explained by Albert Einstein by assuming that:
(A) light is a wave.
(B) light is a particle.
(C) an electron behaves as a wave.
(D) an electron behaves as a particle.
(E) light does not interact with matter.
21. The kinetic energy of photoelectrons depends on the:
(A) speed of light.
(B) angle of illumination.
(C) intensity of the light.
(D) number of incident photons.
(E) photon frequency.
22. A scientist is trying to eject electrons from a metal by shining a light on it, but none are coming out. To eject electrons, she
should change the light by,
(A) decreasing the frequency (B) increasing the frequency, (C) increasing the intensity, (D) increasing the wavelength
23. The maximum kinetic energy of photoelectrons depends on which of the following?
I. The light intensity
II. The frequency of the light
III. The material of the photoelectric cell
(A) Only I (B) Only II (C) Only III (D) Only I and II
(E) Only II and III
24. The photoelectric effect explains :
(A) The wave nature of light (B)The particle nature of light (C) The wave properties of an electron (D) The particle properties of
an electron (E) The atomic structure
25. A measurement of the photoelectric effect for a copper metal plate yields the
result in the graph. The best linear fit yields a slope of
and
a cut-off frequency value
Hz.
i) Explain in one or two sentences why no photoelectrons are observed for
ii) Determine Planck’s constantant the work function of copper from this
measurement (both in SI units).
26. We would like to determine if it is possible to observe the equivalent of the
Compton effect for a target proton rather than a target electron. Calculate the
maximum fractional frequency shift for an incident photon of wavelength
scattering off a proton initially at rest.
You may use a result known for a target electron in combination with a physical argument.
27. The Compton Effect supports which of the following theories?
(A) Special Theory of Relativity. (B) Light is a wave.
(C) Thomson model of the atom.
(D) Light is a particle.
(E) The Coulomb force.
28. A green photon collides with a stationary electron. After the the collision the photon color is
(A) unchanged
(B) shifted toward red (C) shifted toward blue
29. Which of the following formulas can be used to determine the de Broglie wavelength?
(A) λ = hmv
(B) λ = h/mv
(C) λ = mv/h
(D) λ = hm/c
(E) λ = mc/h
30. Which one of the following objects, moving at the same speed, has the greatest de Broglie wavelength?
(A) Neutron
(B) Electron
(C) Tennis ball
(D) Bowling ball
(E) Alpha particle
31. An electron has the same de Broglie wavelength as an 810-nm photon. What is the speed of the electron?
32. A proton has a speed of 2.3 × 104 m/s. What is the energy of a photon that has the same de Broglie wavelength as the proton?
33. Light of wavelength 105 nm falls on a metal surface for which the work function is 5.00 eV. What is the minimum de Broglie
wavelength of the photoelectrons emitted from this metal?
34. Which one of the following objects moving at the same speed is associated with a greatest wavelength?
(A) Neutron
(B) Electron
(C) Tennis ball
(D) Bowling ball
(E) α- Particle
35. An electron and a photon each have a wavelength of
. Find the following quantitites for each (Use de Broglie Postulates
and ignore relativistic effects):
a) momentum
b) energy, in units of eV
36. The de Broglie wavelength of a particle is important in design of experiments based on phenomena such as particle diffraction.
To see why first evaluate de Broglie wavelength of
(1) a 144 eV electron (
)
(2) a 1 eV electron
(3) a 1 eV proton (
(4) a 1 eV alpha particle (
)
)
Now decide which of these particles would be most suitable for use in a crystal diffraction experiment in which crystal spacing is
on order of
37. The electron charge was measured for the first time in the:
(A) Cathode ray experiment.
(B) Photoelectric effect experiment. (C) Oil drop experiment. (D) Electron diffraction from
aluminum foil.
(E) Compton effect experiment.
38. A neutron has almost 2000 times the rest mass of an electron. Suppose they both have 1 ev of energy. How do their
wavelengths compare?
(A) both same (B) neutron wavelength < electron wavelength (C) neutron wavelength > electron wavelength
39. A photon can disappear producing an electron and proton, this phenomenon is called?
(A) Interference of light (B) Diffraction of X-Rays (C) Pair production (D) Scattering of electrons (E) Annihilation
40. When a positron (anti-electron) collides with an electron they disappear producing photons, this phenomenon is called?
(A) Interference of light (B) Diffraction of X-Rays (C) Pair production (D) Scattering of electrons (E) Annihilation