Download Modern physics 2330

Modern physics 2330
Second Midterm Exam.
Time: One Hour
The Islamic University of Gaza
Department of Physics
.........................................:‫ الرقم الجامعي‬....................................................................:‫االسم‬
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Q1 Indicate (√ ) for true statement and (× ) for false statement.
1- ( ) A black body is defined as an object that absorbs all the electromagnetic
radiation falling on it and consequently appears black.
2- ( ) In certain situations light exhibits wave properties like diffraction and
Compton Effect.
3- ( ) The photoelectric effect takes place only if the energy of the incident
electrons exceeds the energy of the photons.
4- ( ) X-rays are produced by bombarding a metal target with energetic electrons
having energies of 50 to 100 KeV.
5- (..) A black hole is an object of sufficiently high density can trap light forever.
6- ( ) Millikan’s oil drop experiment is inaccurate because it is difficult to
measure the speed of drop.
7- (..) Thompson cloud chamber experiment is inaccurate because the theory
applies only to a single particle, and the particles are all assumed to be
identical.
8- ( ) The number, strength, and exact position of the lines in the spectrum of an
element depend only upon temperature.
9- ( ) For large quantum numbers “n”, the discrete energy spectrum goes into a
continuous spectrum.
10- ( ) According to de Broglie, the electron of the Bohr atom forms a standing
h
wave around the nucleus with   .
p
11- ( ) Davisson-Germer experiment (1927) is a direct experimental proof that the
electron charge is, e=1.6x10-19C.
12- ( ).The electron of the Bohr atom forms a standing wave around the nucleus.
13- ( ) The Heisenberg uncertainty principle states that, position and conjugate
momentum can not be measured simultaneously with any degree of accuracy.
14- ( ) A wave packet is a superposition of many plane waves.
15- ( ) Double slit experiment shows that it is impossible to measure both the
particle and the wave properties simultaneously.
Q2 The Planck radiation Formula is given by
8h
f3
u ( f , T )  3 hf / kT
, where h is Planck’s constant, f the frequency, k:
c e
1
Boltzmann’s constant, and T the temperature.
Discuss the limiting cases for low and high frequencies.
Q3 Derive Stefan-Boltzman law
etotal
2 5 k 4 4

T , which states that the total intensity of a blackbody radiation
15 c 2 h 3

x 3 dx  4

is proportional to T4. (You may need the integral  x
)
15
e

1
0
Q4 Discuss Rutherford atomic model.