Final, Thursday, August 16, 2012
PH204
For Dr. Harold Williams
Your Name:
1-Worth 4 points total. Chapter 27: Relativity, section 27.3 Einstein’s Principle of
Relativity. An out of control alien spacecraft is diving into a star at a speed of 2.5x108
m/s. At what speed relative to the spacecraft is the starlight approaching.
2-Worth 4 points total. Chapter 27: Relativity, section 27.9 Relativistic Momentum. a)Worth 2 points. An electron is accelerated to 0.99c. What is the electrons momentum?
The mass of a proton is 1.67x10-27 kg.
b) Worth 2 points. What factor does the protons momentum exceed its Newtonian
momentum?
3)-Worth 25 points total. 24.4 and 25.3 Magnetic Flux: A solenoid 100 meters long and a
diameter of 5 meters has 20,000 turns with a 4 A current is surrounded by a loop that is 1
km in diameter centered perpendicular to the solenoid. a)-Worth 2 points. What is the
magnetic flux in the loop?
b)-Worth 2 points. The loop is tilted 15 degrees. What is the magnetic flux now?
c)-Worth 2 points. 25.4 Faraday’s Law. The loop is tilted 15 degrees in 2 minutes. This
is some sort of science fiction movie device. What is the voltage induced in the 1 km
diameter loop by the 15 degree rotation in 3 minutes.
d)-Worth 3 points. 22.4 Connecting Potential and Current. The 1 km diameter loop
is made of copper wire, which has a resistivity of 1.7x10-8 ohm meters and a
diameter of 1 centimeter. What is the resistance in the wire?
e)-Worth 4 points. 22.4 Connecting Potential and Current. How much current flows
in the loop during the 2 minutes, and in what direction relative to the magnetic field
in the solenoid. Draw a picture with an arrow representing the direction of current.
f)-Worth 2 points. How much power is generated during the 2 minutes the loop is
titled 15 degrees with respect to the solenoid?
g)-Worth 2 points. How much charge is moved during the 2 minutes?
h)-Worth 4 points. 26.6 Inductance and Inductor Circuits. What is the inductance in
Henrys of the loop and solenoid during this motion?
i)-Worth 2 points. RL lab demo equation applied. What is the time constant for this
loop inductor?
j)-Worth 2 points. What speed does the electric field, which moves the current in
the loop move at?
4) Worth 4 points. Chapter 28 Quantum Physics, section 28.2 Photoelectric Effect section
and Photoelectric Effect lab. Electrons in a photoelectric-effect experiment emerge from
a copper surface, which has a work function of 4.6 eV, with a maximum kinetic energy of
2.2eV. What is the wavelength of the light?
5) Worth 6 points. 25.6 Properties of Electromagnetic Waves (polarization). Given
unpolarized light and perfect polarizers, after the first polaroid filter what is the intensity
of light? If the second polarizer is at a 45 degree angle with respect to the axis of the
first polaroid filter what is the intensity after the second polaroid filter? The third
polaroid filter is oriented such that without the second polaroid filter the angle is 90
degrees and no intensity gets through with the second filter removed from beyond the
third filter. How much gets beyond the third polaroid filter with all three polaroid filters
in and the orientation as stated? We saw this demonstrated in class! This is actually a
two state quantum mechanical system with the wave function regenerated being
demonstrated! This is actually deep physics! Draw a diagram showing your answer in
terms of I coming into the first polaroid filter unpolarized and then after the first filter,
then the second filter, and then the after the third filter. Don’t panic just do it!
6) Worth 12 points total. 25.8 The EM Spectrum. a)-Worth 4 points. The spectrum of the
sun has a wavelength peak of around 530nm, what is the effective temperature of the sun
if it were a perfect blackbody radiator? (The sun is only an approximate blackbody
radiator, it has an absorptive atmosphere.)
b)-Worth 4 points. At this temperature how much power/area in Watts/m2 comes off of
the sun?
c)-Worth 4 points. Given that the sun is round with a radius of 6.96x108 meters
how much power does it radiate, approximately, in watts?
7)-Worth 2 points. 238U decays via alpha decay to what element with what atomic mass?
8)-Worth 4 points. 238U decay constant  is approximately 6.4459x109 years or a t1/2 the
decay half life is 4.469x109 years. How long does it take for 238U to decay to 1/16 of its
original amount?
9-Worth 9 points. From first test, Lens lab. A plane on one side and convex on the other
side glass lens has an index of refraction of n=1.6 and the convex side has a radius of
curvature of 60 cm, what is the focal length of the lens. Please use the corrected
formulae we went over in class not the incorrect one given in the lab manual
10)-Worth 10 points total. Chapter 18. A convex lens has a focal length of 50 cm and
an object is placed in front of it 70 cm. Worth 3 points. What is the image distance?
Worth 2 points. What is the magnification of the image?
Worth 2 points. If the object is 3cm high what is the image height?
Worth 1 point. Is the image real or virtual?
Worth 1 point. Is the image up right or inverted?
Worth 1 point. Please draw a ray diagram and label everything clearly!
11)-Worth 8 points.
A pair of charged conducting plates produces
a uniform field of 12,000 N/C, directed to the right, between the plates. The separation of
the plates is 40 mm. In the figure, a doubly ionized Helium 4 nucleus, an alpha particle,
(of mass 4.002 u, atomic mass units u, u=1.661  10-27 kg) is projected from plate A,
directly toward plate B, with an initial velocity of 0 m/s. The velocity of the doubly
ionized Helium 4 nucleus as it strikes plate B is?
12)-Worth 10 points. The figure shows two 10.0 g spheres suspended from 1.0-m-long
threads. The spheres repel each other after being charged with an equal charge on both.
The angle θ has been measured and it is 7 degrees. What is the charge on each of the
spheres? Can you say anything about the sign of the charge positive or negative from the
information given?
13-2 points. How does the Heisenberg Uncertainty relationship help explain how
come negative electrons do not spiral into the positively charged nucleus in a very
short time?