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COLLEGE OF ENGINEERING
SPECIAL SEMESTER 2007/2008
PROGRAMME
:
FOUNDATION
SUBJECT NAME
:
PHYSICS III
SUBJECT CODE
:
PHYF 132
DATE OF EXAMINATION :
JUNE 2008
DURATION
:
2 HOURS
VENUE
:
LIBRARY EXAM HALL
Arahan-arahan kepada calon:
1. Jawab semua soalan di Bahagian A dan mana-mana 3 soalan di Bahagian B.
2. Jawab semua soalan dengan menggunakan pen.
JANGAN BUKA KERTAS SOALAN INI SEHINGGA ANDA DIARAH
BERBUAT DEMIKIAN
Instructions to candidates:
1. Answer all questions in Part A and any 3 questions in Part B.
2. Answer all questions using pen.
DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE INSTRUCTED TO DO SO
KERTAS SOALAN INI MENGANDUNGI 7 MUKA SURAT BERCETAK
TERMASUK MUKA SURAT INI.
THIS QUESTION PAPER CONSISTS OF 7 PRINTED PAGES INCLUDING THIS
PAGE.
1
CONSTANTS
Speed of light, c  3.00 108 m/s ; nair = 1.00; nice = 1.31; nglass = 1.50; αCu = 17  106
C 1; Rydberg’s constant, R = 1.097 × 107 m1; Planck’s constant, h = 6.626 10 34
o
Js; 1 liter = 103 m3; 1 atm = 1.013  105 Pa; CV, argon = 12.5 J/mol·K ; Cp, argon = 20.8
J/mol·K; k = 8.99  109 Nm2C-2; e = 1.602 1019 C; Bohr radius, ao = 0.0529 nm;
me  9.1110 31 kg
Part A: Answer all questions (Each question worth 2 marks)
1. A copper rod has a length of 20.0 m when the temperature is 0.00oC. What is its
length when the temperature is 60.0oC?
2. Find the speed of the wave function, y (x, t) = (0.150 m) sin (0.800x – 50.0t),
where x and t are in SI units.
3. A rope fixed at both ends, oscillates in a second-harmonic standing wave pattern.
The displacement of the rope is given by;
 
y  (0.100 m) sin  x  cos(12.0 t ) ,
2 
Where, x is in meters, and t is in seconds. Calculate
(a) the length of the rope, and
(b) the speed of the waves on the rope.
4. A cubical block of ice 50.0 cm on a side is placed on a level floor over a speck of
dust. Find the location of the image of the speck as viewed from above.
2
5. Figure 1 shows a beam of light enters a rectangular block of plastic at point A
with an angle of θ1 = 48.0o. The beam then is refracted at an angle of θA and
emerges at point B at an angle of θ2 = 70.0o. Calculate the value of θA.
[Hint: sin (A±B) = sin A cos B ± cos A sin B]
Air
θ1
Plastic
A
θA
B
θ2
Air
Figure 1
6. A thin lens has a focal length of 25.0 cm. Find the image distance and describe the
image when the object is placed at (a) 26.0 cm and (b) 24.0 cm in front of the lens.
7. What is the distance between the fourth bright fringe and the second dark fringe
on a screen of 18.0 m from two double slits of 0.0500 mm apart. The slits were
illuminated with 580 nm light?
8. What is the distance from the central maximum on the screen if the average
intensity is 70.0 % of the intensity from the central maximum? Given the two slits
are illuminated with green light ( = 540 nm) and the slits are 0.0500 mm apart
with the distance to the screen of 1.50 m.
9. A light of wavelength λ0 = 650 nm is required to eject electrons from the surface
of a metal. Determine the work function, W for the metal.
3
10. Determine the wavelength and energy of the photon emitted from a hydrogen
atom when the electron jumps from the second excited state to the first excited
state.
Part B: Answer any 3 questions (Each question worth 10 marks)
1. (a) Figure 2 shows a cycle consisting of five paths: AB and DE are isothermal at
the temperature of 300 K and 100 K respectively. BC is adiabatic with work of
5.00 J, EA is adiabatic with a change in internal energy of 8.00 J.
i. What is the change in internal energy of the gas along path CD (isobaric)?
[3]
ii. What is the work done on the gas along path AB if the work done by path
CE is +10.0 J and the total work done of the gas for the whole process is
+9 J?
[3]
p
A
B
E
D
C
V
Figure 2
(b). A cylinder contains 6.00 mol of argon gas at temperature of 290 K.
i. If the gas is heated at constant volume, how much energy must be
transferred by heat to the gas for its temperature to rise to 600 K?
[2]
ii. How much energy must be transferred by heat to the gas at constant
pressure to increase the temperature to 400 K?
4
[2]
2. (a) Adjacent antinodes of a standing wave on a string are 15.0 cm apart. A particle
at an antinode oscillates in simple harmonic motion with amplitude of 0.850
cm and period of 0.0750 s. The string lies along the + x axis and is fixed at
x = 0.
i. Calculate the wavelength, amplitude, and speed of the two traveling waves
that form this pattern.
[3]
ii. Find the maximum transverse speed of a point at an antinode.
[1]
iii. What is the shortest distance along the string between a node and an
antinode?
[1]
(b) In Figure 3, a beam of monochromatic light reflects and refracts at point A on
the interface between medium 1 with index of refraction, n1 = 1.33 and
medium 2 with index of refraction, n2 = 1.77. The incident beam makes an
angle of 50.0o with the interface. The light that enters medium 2 at point A
then reaches point B on the interface between medium 2 and medium 3, which
is air (n = 1.00) as shown in Figure 3.
i. Find the angle of reflection at point B.
[1]
ii. Find the angle of refraction at point B.
[2]
iii. Find the critical angle on the interface between medium 2 and medium 3.
[2]
θ1
θ1’
n1
50.0o
A
n2
θ2 θ2’
θ2
B
n3
θ3
Figure 3
5
3. (a) The image formed by a spherical mirror may be larger, smaller, or equal in
size to the object. If the magnification of the mirror is negative, describe the
image of the object.
[2]
(b) A monochromatic red light of wavelength λ = 640 nm passes from air into a
glass plate of refractive index, nglass = 1.50. Determine the wavelength of the
light inside the glass plate.
[2]
(c) A coin rests on the bottom of a container filled with water refractive index,
nwater = 1.33. The apparent distance of the coin from the surface is 9.0 cm.
Determine the depth of the water.
[2]
(d) Figure 4 shows a thin glass (nglass = 1.50) of converging lens for which the
radii of curvature are R1 = 15.0 cm and R2 = –12.0 cm. To the left of the lens is
a cube having a face area of 100 cm2. The base of the cube is on the axis of the
lens, and the right face is 20.0 cm to the left of the lens as shown in the Figure
4. Determine the focal length of the lens and draw the image of the square face
formed by the lens.
[4]
Figure 4
6
4. (a) A student studying the photoelectric effect from two different metals records
the following information:

The stopping potential for photoelectrons released from metal 1 is 1.48 V
larger than that for metal 2, and

The threshold frequency for metal 1 is 40.0% smaller than that for metal 2.
Determine the work function for each metal.
[4]
(b) For a hydrogen atom in its ground state, use the Bohr model to compute:
i. the orbital speed of the electron.
ii. the kinetic energy of the electron.
iii. the electric potential energy of the atom.
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[6]