May 1998
Physics 265
Final Exam
Name _______________________
Do all work on these sheets. Try all questions; do not spend too much time
on any one problem. Credit may be subtracted if your work is disorganized,
illegible, incomplete, lacks proper accuracy of if methods are clearly
indicated. Bonus Yes
No.
___________________________________________________________________________
Multiple Choice (3 points each)
_____ 1.
Natural radioactive rays that will not be deflected by a magnetic
field are: (a) alpha rays, (b) beta rays,
(c) gamma rays.
_____ 2.
The concept of the atomic nucleus resulted from the work of
(a) Bohr, (b) Thompson, (c) Rutherford, (d) Geiger.
_____ 3.
The conservation of nucleons and the conservation of charge apply
to: (a) only alpha decay, (b) only beta decay, (c) only
gamma decay, (d) all nuclear processes.
_____ 4.
A space ship traveling at 0.5c with respect to a space station
turns on his headlight as it approaches the station. An observer
on the space station will determine the velocity of light from
the space ship to be: (a) c, (b) 1.5c, (c) 1.1c,
(d) 0.75c, (e) 0.5c.
_____ 5.
Which is not an essential for laser action? (a)
inversion, (b) phosphorescence, (c) pumping,
emission.
_____ 6.
What is necessary to stop beta particles? (a) air alone,
(b) paper, (c) metal foil, (d) thick metal.
_____ 7.
When
(a)
207Pb
208Pb,
population
(d) stimulated
is bombarded with neutrons, it can change into:
(b) 209Pb, (c) 208T , (d) 208Bi.
_____ 8.
A plane mirror (a) has greater image distance than object
distance, (b) produces a virtual, upright, unmagnified image,
(c) reverses top and bottom.
_____ 9.
What is the source of the energy the sun radiates to us?
(a) chemical reactions, (b) nuclear fission, (c) nuclear
fusion, (d) magnetic explosions, (e) cosmic rays.
_____10.
Magnetic fields affect: (a) only charges at rest, (b) only
charges in motion, (c) both charges in motion and charges at
rest, (d) neither charges in motion nor charges at rest.
_____11.
To measure the current through a circuit element, an ammeter is
connected (a) in series with the element, (b) in parallel with
the element, (c) between the high potential side of the element
and ground.
_____12.
The potential difference across each resistor in a circuit must
be the same when they are connected in (a) series,
(b)
parallel,
(c)
series-parallel,
(d)
parallel-series.
Physics 265
2.
_____13.
Equipotential surfaces are (a) parallel to the electric field,
(b) perpendicular to the electric field, (c) at any angle with
respect to the electric field.
_____14.
The electronvolt (eV) is a unit of: (a) power, (b)
(c) energy, (d) force, (e) potential difference.
_____15.
John observes a fish below the surface of a lake. Looking down
from above into the water the distance the fish appears below the
surface is: (a) less than the fish's actual distance,
(b) equal to the fish's actual distance, (c) greater than the
fish's actual distance.
_____16.
If you push a magnet into a coil of wire that is part of a closed
circuit: (a) a charge appears in the coil, (b) an electric
field radiates away from the coil, (c) an electric current
flows in the coil, (d) nothing happens since the circuit is
closed.
_____17.
Suppose Supuman hurls a meter stick horizontally with a velocity
of 0.8c with respect to the Earth. What will be the length of
the meter stick as observed by a person at rest with respect to
the earth? (a) 1.67m, (b) 1.33m, (c) 1.00m, (d) 0.80m,
(e) 0.60m.
_____18.
The lens of the eye forms an image on the retina that is:
(a) real and erect, (b) real and inverted, (c) virtual and
erect, (d) virtual and inverted.
_____19.
According to the Pauli exclusion principle, no two electrons in
an atom can have the same: (a) spin, (b) speed, (c) orbit,
(d) set of quantum numbers.
_____20.
What is the resistance of John's 24.0W, 12.0V light bulb?
(a) 0.5 ohms, (b) 2 ohms, (c) 6 ohms, (d) 24 ohms.
charge,
Problems (20 points each)
1.
John loved physics so much he wanted a framed photo of his physics
book, so he used a simple camera with a single converging lens of
focal length 0.045m. He placed his 26.0cm tall physics book 1.50m
from the camera. (a) Assuming sharp image on film, how far is film
from lens? (b) What is image height? (c) Nature of image?
(real/virtual; erect/inverted).
Physics 265
3.
2.
Cindy uses the spectrometer with 700nm (red) light and observes in the
second-order spectrum the line is deviated at an angle of 20o. (a)
What is the grating constant? (b) How many lines per centimeter does
the grating have? (c) What angle would be observed in third order?
3.
Complete the following nuclear decay equations
(a)
8Be
  + _____
(c)
4
(b)
29Na
11
23Na
+   _____
11
 - + _____
(d)
38K
19
+ 1H  ____ +
1
38Ca
20
(e)
For the isotopes of uranium (all unstable) that have mass numbers from
232 to 239, what are the numbers of protons _____, electrons _____ and
neutrons ______________ in a neutral atom of each isotope?
Physics 265
4.
Fusion appears to be the ideal energy source of the future. Enough
deuterium exists in the oceans to supply our needs for centuries.
Calculate the energy released in the following fusion reactions that
begin with deuterium:
(a)
2H
1
(b)
3He
2
5.
4.
+ 2H 
1
3He
+
2
+ 3He 
2
1n
0
4He
2
+ 2 1H
1
In 1893 Pierre & Marie Curie isolated about 10.0mg of radium 226
(half-life ~ 1600 yr) from 8 tons of pitch blende. If this sample had
been placed in a museum, how much of the radium would remain in the
year 2000?
Physics 265
5.
6.
At an Army research center Cindy observed electrons accelerated from
rest through a potential of 50.0V. Calculate (a) speed of electron,
(b) de Broylie wavelength of electron, (c) grating width to produce
a diffraction on pattern with first maximum at 8.20o.
7.
According to the Bohr theory the hydrogen atom in an excited can have
a radius of 0.84668nm. (a) What is the principal quantum number for
this state? (b) What is its speed in this state? (Keep 5
significant figures)