Engineering physics-Questions

Study Material
Engineering Physics
G. K. Sahu
SchoolofEngineering
Centurion
UNIVERSITY

QUESTION BANK: ENGINEERING PHYSICS, SUBJECT
CODE: BSPH1203
[For B.Tech, 1st
Semester CSE, 2nd
Semester ECE, EEE, EE of CENTURION UNIVERSITY
OF TECHNOLOGY AND MANAGEMENT]
Topic- Electron theory of solids, Hall Effect, semiconductor
and superconductor
Section – A (Short type question)
1. In two materials the energy gap between the conduction band and valence band is =1eV
and =5eV. Classify the materials electrically. (BPUT-2005)
2. What type of semiconducting material is produced when an alloy of aluminium and
germanium in the ratio 1:106
is prepared? (BPUT-2007)
3. Show graphically the variation of resistivity of a pure metal with temperature according to
classical free electron theory. (BPUT-2005)
4. Why does conductivity of metals decreases at higher temperature? (BPUT – 2005)
5. Write Wiedemenn-Frantz law.
6. Draw the band diagram of insulators and conductors. (BPUT-2006)
7. Give the band diagrams of insulators, conductors and semiconductors. (BPUT-2005,07)
8. Mention one similarity and one dissimilarity between energy level band diagram of silicon
and diamond(BPUT-2006)
9. Write down the expression for Lorentz number (BPUT – 2005)
10. Prove that the probability of occupancy of an energy level by the electrons below Fermi
level at 0o
C is 1.(BPUT-2005)
11. Show that all the energy levels of a material below the Fermi level at 0K are filled up by
electrons. (BPUT-2007)
12. What is Hall Effect? (BPUT – 2005)
13. Is Hall Effect affected by sign of the charge carrier? Justify your answer. (BPUT-2005)
14. What are superconductors? Give any two examples.
15. What type of magnetism is developed in a superconducting material below its critical
temperature? (BPUT-2005)
16. Indicate the type of superconductivity observed in Aluminum metal and Niobium-
Zirconium alloy.(BPUT-2004)
17. Show the variation of resistance verses the temperature of a superconductor and normal
conductor. (BPUT-2006)
18. What type of magnetism is developed in a superconductor when its temperature is lowered
below its critical temperature? (BPUT-2006)

19. Plot the variation of critical magnetic field with temperature of a superconducting material.
(BPUT-2006)
20. What are Cooper pairs? (BPUT-2005)
21. What are high temp superconductors? Give two examples.
22. Define Meissner effect. (BPUT-2004)
23. Show that electric field inside a superconductor is zero. (BPUT-2005)
24. Write any two applications of superconductor. (BPUT-2005)
25. Write any two medical applications of superconductor. (BPUT-2005)
26. Show that electric field inside a super conductor is zero. (BPUT-2005)
27. Electrical conductivity of insulators is the range _____________.
10-10(Ω-mm)-1 (b) 10-10(Ω-cm)-1 (c) 10-10(Ω-m)-1 (d) 10-8(Ω-m)-1
28. Units for electric field strength
(a) A/cm2 (b) mho/meter (c) cm2/V.s (d) V/cm
29. Energy band gap size for semiconductors is in the range ________ eV.
(a)1-2 (b) 2-3 (c) 3-4 (d) > 4
30. Energy band gap size for insulators is in the range ________ eV.
(a)1-2 (b) 2-3 (c) 3-4 (d) > 4
31. Flow of electrons is affected by the following
(a) Thermal vibrations (b) Impurity atoms (c) Crystal defects (d) all
32. Not a super conductive metallic element
(a) Fe (b) Al (c) Ti (d) W
33. Fermi energy level for intrinsic semiconductors lies
(a) At middle of the band gap (b) Close to conduction band
(c) Close to valence band (d) None
34. Fermi energy level for p-type extrinsic semiconductors lies
35. Fermi energy level for n-type extrinsic semiconductors lies
36. Not an example for intrinsic semiconductor
(a) Si (b) Al (c) Ge (d) Sn
37. In intrinsic semiconductors, number of electrons __________ number of holes.
(a) Equal (b) Greater than (c) Less than (d) Can not define
38. In n-type semiconductors, number of holes __________ number of electrons.
39. In p-type semiconductors, number of holes __________ number of electrons.
(a) Equal (b) Greater than (c) Less than (d) Twice
40. Mobility of holes is ___________ mobility of electrons in intrinsic semiconductors.
41. Fermi level for extrinsic semiconductor depends on
(a) Donor element (b) Impurity concentration (c) Temperature (d) All

(ANSWRS FROM 27-41)
27. a
28. c
29. b
30. c
31. d
32. b
33. c
34. b
35. b
36. a
37. c
38. d
39. a
40. d
41. d
Section – B (Descriptive type questions)
42. Write the main postulates of classical free electron theory and derive the expression for
electrical conductivity of a material. Also write the advantages and draw backs of this
theory.
43. What are the postulates of Drude-Lorentz theory of metals? (BPUT-2006)
44. Discuss the advantages and disadvantages of classical free electron theory of metals.
(BPUT-2005)
45. Derive an expression for the electrical conductivity of a material in terms of relaxation
time. (BPUT-2006)
46. Differentiate between n- and p- type extrinsic semiconductors with suitable examples.
(BPUT-2004)
47. What is Hall effect? How you will determine the mobility of electrons in germanium
knowing only the resistivity and Hall coefficient of it? (BPUT-2005)
48. Explain the phenomenon of Hall Effect. Discuss the method of identifying an unknown
piece as n-type semi conductor.
49. Distinguish between soft superconductor and hard superconductor. (BPUT-2007)
50. Distinguish between Type-I and Type-II superconductors. (BPUT-2005)
Section – C (Problems)
51. The density and atomic weight of cu are 8900 kg m-3
and 63.5. The relaxation time of
electrons in Cu at 300K is 10-14
S. Calculate the electrical conductivity of copper.
52. A conduction wire has a resistivity of 1.54 x 10-8
ohm m at room temperature. The Fermi
energy for such a conductor is 5.5ev. there are 5.8 x 1028
m-3
conduction electron per m3
.
Calculate.
a. The relaxation time and the mobility of the electrons.
b. The av.Drift velocity of the electrons when the electric field applied to the conductor
is 1Vcm-1
.
c. The velocity of an electron with Fermi energy.
d. The mean free path of the electron.
53. Calculate the conductivity of Al at 250
C using the following data. Density of Al = 2.7g
cm-3
, at weight of Al =27 and relaxation time of electrons = 10-14
s.
54. Calculate the Fermi energy in Zinc at 0K. The density and atomic wt. of Zinc is 7.14g/cm3
and 65.38amu. (BPUT-2005)
55. The thermal and electrical conductivities of Cu at 200
C are 390w m-1
K-1
and 5.87 x
107
ohm -1
m-1
respectively. Calculate Lorentz no.

56. Relaxation time of electrons in copper is 2.5x10-14
s. There are 8.4x1028
number of
conduction electrons per unit volume. Find the electrical conductivity of copper as per the
classical free electron theory of metals. (BPUT-2007)
57. The electron and hole mobility for silicon are 0.14 and 0.048 m2
/V-s respectively at room
temperature. If the hole concentration at this temperature is 1.33 x 1016
m-3
, calculate its
conductivity at room temperature. [Given |e| = 1.6 x 10-19
C]. (BPUT-2004)
58. Calculate the electrical conductivity of intrinsic silicon at 1500
C. Given ni = 4 x 1019
m-3
,
µe = 0.06 m2
/Vs and µh = 0.022m2
/Vs.
59. The following data are given for an intrinsic Ge at 300K. Calculate the conductivity of the
sample. (Given ni = 2.4 x 1019
m-3
, µ= 0.39m2
V-1
s-1
, µn = 0.19 m2
V-1
s-1
)
60. The concentration of free electrons in germanium crystal is 2x1019
electrons/m3
.and the
nobilities of electrons and holes respectively are 0.36m2
V-1
s-1
and 0.17 m2
V-1
s-1
. Calculate
the current produced in a germanium crystal having cross sectional are 2cm2
,
length0.2mm, under a potential difference of 2V. (BPUT-2007)
61. Calculate the electrical and thermal conductivities for a metal with relaxation time 10-14
at
300
K. Also calculate the Lorentz no. by the above result. (Density of electrons = 6 x 1028
m-3
).
62. The Fermi energy of silver at 0 K is 5.51eV. What is the average energy of free electrons
in silver at 0 K. (BPUT-2006)
63. In a material transition occurs between a metastable state and an energy level of 0.24 eV
and the wavelength of radiation emitted is 1100 nm. Calculate the energy of the metastable
state. (BPUT-2006)
64. Calculate the Fermi energy in Zinc at 0K. The density and atomic wt. of Zinc is 7.14g/cm3
and 65.38amu. (BPUT-2005)
65. Find the temperature at which there is 1% probability that an electronin a solid will have
an energy 0.5eV above the Fermi energy. (e=1.6x10-19
C and kB= 1.38x10-23
J/K) (BPUT-
2005)
66. Phosphrous is added to high purity silicon to give a concentration of 1023
m-3
of charge
carriers at room temperature. Calculate the conductivity at room temperature. What type of
semiconductor is this material? (BPUT-2005)
67. The Fermi energy in copper at 0K on the assumption that each coper atom contributes one
electron to the electron gas is 7.04eV.Calculate the Fermi energy and average energy of an
electron in metal at 300K. (BPUT-2005)
68. The concentration of free electrons in copper is 8.4x1028
m-3
. Calculate the hall coefficient.
(BPUT-2006)
69. The hall coefficient and conductivity of cu at 300K have been measured to be -0.55 x 10-10
m3
A-1
s-1
and 5.9 x 107
ohm -1
m-1
respectively. Calculate the drift mobility of electron in
copper.
70. An n-type semiconductor specimen has Hall coefficient RH = 3.66 x 10-11
m3
A-1
s-1
the
conductivity of the specimen is found to be 112 x 107
ohm -1
m-1
. Calculate the charge
carrier density ne and electron mobility at room temperature.
71. A current of 200A is established in a rectangular slab of copper of width 2cm and 1.0mm
thickness. A magnetic field of induction 1.5T is applied perpendicular to both current and
the plane of the slab. The concentration of free electrons in copper is 8.4x1028
m-3
.
Calculate the Hall voltage across the slab. (BPUT-2005, 07)

72. The critical temperature for certain superconducting material with isotopic mass 202amu is
4.153K. Calculate its critical temperature when its isotopic mass becomes 200 amu.
(BPUT-2005)
73. The radius of an indium wire is 6mm. The critical temperature is 3.4K and the critical
magnetic field is 29.3x10-3
Tesla at 0K for indium.Calculate the critical current density in
the wire at 2K. (BPUT-2006)
74. It is found experimentally that superconducting critical temperature of indium is 3.4 K and
critical magnetic induction at 0K is 29.3x10-3
T. What will be the critical current density of
indium wire of radius 5mm at 4K? (BPUT-2005)
75. It is found experimentally that superconducting critical temperature of lead is 7.193 K and
critical magnetic induction at 0 K is 80.3 X 10-3
Tesla. What will be the critical current
density of lead wire of radius 5 mm at 4 K? (BPUT-2006)
76. In n-type semiconductor, the Fermi level lies 0.3 eV below the conduction band at 300 K.
If the temperature is increased to 330 K, calculate the new position of the Fermi level
assuming that concentration of carriers does not change with temperature. (BPUT-2006)
Topic- Optical properties of materials, Laser, Optical fibers
Section – A (Short type question)
77. What is the full form of LASER? State its different applications.(BPUT-2004)
78. What properties of LASER differentiate it from other light source?
79. Ruby LASER is an example of --------------
a. Two level, b. Three level, c) Four level, d) None
80. Among the following LASERS which emits the largest wave length radiation
a.) Ruby LASER, b) CO2 LASER c) Semiconductor LASER, d) He-Ne LASER.
81. LASER is produced due to Stimulated emission, b) Stimulated absorption, c) Spontaneous
emission, d) all the above.
82. In LASER production, population inversion takes place at (a) Ground state, b) Excited
state, c) Meta stable state , d) Stable state.
83. What is the necessary and sufficient condition for LASER production.
84. Define saturation intensity?
85. Write the use of two mirrors in LASER system.
86. Define temporal and spatial coherence.
87. What do you mean by optical properties of material? (BPUT-2005)
88. Distinguish between spontaneous emission, induced absorption and induced emission.
(BPUT-2005)
89. Explain how lasers are useful in computer system. (BPUT-2006)
90. How LASERs are in use to improve the living conditions in the world. (BPUT-2007)
91. How optical fibers are in use to improve the living conditions in the world?(BPUT-2004,
06, 07)
92. Give statement of the basic principle involved in the functioning of an optical fiber.
(BPUT-2005)

93. Draw the cross sectional views of an optical fiber and show the different components of
the optical fiber in it. (BPUT-2006)
94. Distinguish between step index multimode fiber and graded index multimode fiber.
(BPUT-2006)
95. What will happen if the refractive index of the core is lesser than that of cladding? (BPUT-
2007)
Section – B (Descriptive type questions)
96. What are optical fibers? Discuss its principle of operation. (BPUT-2005)
97. What is acceptance angel in optical fiber? Derive an expression for the numerical
apperature of a step index optical fiber in terms of its refractive indices of core and
cladding. (BPUT-2006)
98. Write the principle of LASER production. (BPUT-2004)
99. Explain how a four level laser system works? (BPUT-2005)
100. What is LASER? Explain the principles of operation of He-Ne LASER. (BPUT-2005)
101. Explain with block diagram the FOCL. (BPUT-2006)
Section – C (Problems)
102. The refractive index of the material is 1.54 and the transmissivity of a dielectric material of 15 mm
thick to a normally incident light is 0.80. Calculate the thickness of the material that will have
transmissivity of 0.7. All the reflection losses are to be included. (BPUT-2006)
103. The dielectric constant of quartz is 1.55. Calculate the refractive index of the material.
(BPUT-2006)
VECTORE CALCULAUS
104. A scalar function is given by f(x, y, z) = 2xy2
+ xyz3
. Evaluate the gradient of the
function at the point (1, 1, 1).(Supp2006)(3marks)
105. Evaluate ∇ q, q = ax2
– 2by + c2
z2
where a, b and are c are constant at (1, -2, 3) (1st
sem 2009) (3)
106. What is physical significance of gradient of a scalar function?(1st
sem 2009) (2)
107. A single turn coil of radius 5cm is placed on a plane paper and magnetic flux, directed
perpendicularly out of the paper varies according to φ = 11t2
+ 7t + 15. What is the
magnitude and direction of induced emf in the coil at time t = 1.5s? (1st
sem
2007)(2marks)
108. Evaluate F
rr
⋅∇ where kxyzjyxixyF ˆˆˆ2 22
++=
r
and i, j, k are unit vectors along x, y& z
directions respectively. (2nd
Sem 2004)(2marks)
109. A vector field is given by jyixF ˆ5ˆ2 +=
r
Evaluate the divergence of the vector.
(Supp2004)(4marks)

110. Evaluate the divergence of the vector field kxzjyixyF ˆ3ˆ2ˆ2 ++=
r
at (1, 1, 0).
(2nd
sem2005)(3marks)
111. Evaluate the divergence of kxzjyixyA ˆ2ˆˆ 2
++=
r
at the point (2, 1, 0) (1st
sem 2005)
112. Evaluate divergence of a position vector. (2nd
sem 2006)(2marks)
113. Define divergence of a vector function in terms of integrals. (2nd
sem 2006)
114. What is the physical significance of curl of a vector function? (2nd
sem 2006)(2marks)
115. Evaluate curl A. Where kxzjyzixyA ˆˆˆ ++=
r
(1st
sem 2003)(2marks)
116. Evaluate r
rr
×∇ where r is the position vector. (1st
sem 2005)(2marks)
117. What is the physical significance of line integral of a vector function? (2nd
sem
2007)(2marks)
118. Evaluate the surface integral for the vector function zyzyyxxzF ˆˆˆ4 2
+−=
r
over the
surface S. where S is the surface of the unit cube bounded by x=0, x=1, y=0, y=1, z=0,
z=1(2nd
sem 2006)(6marks)
119. State Gauss divergence theorem in vector calculus. (Supp2004) (1st
sem 2005)(2marks)
120. Using Gauss divergence theorem, prove that the volume of a sphere of radius r is 4/3
(πr3
) (1st
sem2004)(5marks)
121. State Stoke’s theorem in vector calculus. (Supp2006)
122. Write the second form of the Green’s theorem. (1st
sem2004)
123. Write Gauss law of electrostatics in a dielectric medium. Obtain its differential form.
(Supp2005)(4marks)
124. State Gauss law in electrostatics. Obtain its differential form in vacuum.
(Supp2006)(4marks)
125. Write the integral and differential form of Gauss’s law in electrostatics in vacuum
(2nd
sem 2004)(4marks)
126. Write down the Maxwell’s electromagnetic wave equations both in differential form. (2
mark,2nd
sem 2010).
127. Write the Maxwell electromagnetic equation in free space, which follow from Gauss
law in electrostatics. (Supp2005)
128. Find the electric field intensity at a distance ‘r’ from a point charge ‘q’ by applying
Gauss law in electromagnetism. (2nd
sem 2007)(2marks)
129. Starting from Faraday’s law of electromagnetic induction, establish the relation,
t
B
E
∂
∂
−=×∇
r
rr
(1st
sem2004)(2marks)
130. What is Faraday’s law of electromagnetic induction? Find out its differential form. (5
mark,2nd
sem 2010)
131. Write the Maxwell’s electromagnetic equation in differential form, which follows from
Faraday’s law of electromagnetic equation. (2nd
sem 2004) (Supp2004)
132. State Ampere’s circuital law and obtain it’s differential form. (2nd
sem2005)(4marks)
133. Write the integral form of the Ampere’s circuital law. (1st
sem 2003)
134. Distinguish between conduction current and displacement current. Give examples.
(2nd
sem 2004) (2nd
sem2005)(Supp2006) (2nd
sem 2007) (4marks) (2 mark,2nd
sem 2010)
135. Derive the relation between displacement current and the magnitude of electric
displacement. (2nd
sem 2006)(2marks)

136. Each plate of a parallel plat capacitor has area 15 cm2
and is being charged. The time
rate of variation of electric field between the two plates of the capacitor is 12.6 x 109
V/ms. Calculate the displacement current flowing between the plates of the capacitor.
(1st
sem 2007)(2marks)
137. What is the S.I unit of electric displacement vector. (2nd
sem 2007)
138. The electric field between two parallel metal plates of area 1 cm2
changes at the rate of
1.2X108
volt/m.sec. Calculate the displacement current. (Supp2005)(3marks)
139. One of the Maxwell’s e-m equations involves the curl of the electric field. Write the
equation & mention the law of electromagnetism which is represented by the
equation.(1st
sem 2005)
140. Write Maxwell’s electromagnetic equations in differential form in a medium in
presence of charge and currents. Identify and state the law of electromagnetism with
which these equations are associated. (1st
sem 2009) (3)
141. Write the Maxwell’s electromagnetic equation in differential form in a medium, in the
presence of charges and currents. Identify and state the laws of electromagnetism with
which these equations are related. (1st
sem 2003)(8marks)
ELECTROMAGNETIC WAVES
142. Write all four Maxwell’s equation in electromagnetic (1st
sem 2007)(2marks)
143. Write the Maxwell’s electromagnetic equation, which follows from the non-existence of
isolated magnetic pole. (2nd
sem2005) (Supp2006) (2nd
sem 2006)(2marks)
144. Write Maxwell’s electromagnetic equations in free space, in presence of charges and
currents. Name each symbol used in the equation. (Supp2004)(6marks)
145. Write Maxwell’s e-m equations in vacuum in the absence of any charge or current.
(Supp2006)(6marks)
146. State the Maxwell’s equation in electromagnetism connecting magnetic field vector and
electric displacement vector. (2nd
sem 2006)(2marks)
147. Starting from Maxwell’s electromagnetic equations in free space, in absence of charge
and currents, obtain the wave equation for electric field. (2nd
sem 2004)(Supp2004)
(4marks)
148. Starting from Maxwell’s electromagnetic equations in vacuum, obtain the wave
equations for the four fields vectors E, D, B and H. (1st
sem 2007)(4marks)
149. Derive electromagnetic wave equation in terms of electric vector when the wave is
passing through vacuum. (1st
sem 2009) (3)
150. Obtain electromagnetic wave equation from Maxwell’s equation in a charge free and
current free region. (1st
sem2004)(6marks)
151. Derive the e-m wave equation in terms of electric vector when the wave is passing
through vacuum. (2nd
sem 2006)(5marks)
152. Derive equation for an electromagnetic wave travelling in a charge free conducting
medium in terms of electric field vector. (4 mark,2nd
sem 2010)
153. Starting from Maxwell’s e-m equation, obtain the wave equation for E in an ionized
medium. Identify the dissipative terms in the equation.
(1st
sem 2005) (Supp2005)(5marks)
154. Write the wave equation for the electric field E in an ionized medium. (2nd
sem 2004)

155. Starting from Maxwell’s electromagnetic equations in free space, obtain the wave
equations in terms of scalar and vector potentials. Mention the Gauge conditions used.
(1st
sem 2003)(6marks)
156. Write the electromagnetic wave equation in free space, in terms of scalar and vector
potential. (1st
sem 2003) (Supp2004) (Supp2005)(2nd
sem2005) (2nd
sem 2006)(3marks)
157. Prove the transverse nature of electromagnetic wave mathematically. (1st
sem 2009) (4)
158. Electromagnetic waves are transverse waves; that means electric vector, magnetic
vector and propagation vector are perpendicular to each other. Prove this
mathematically. (2nd
sem 2007)(3+3marks)
159. Imagine an 3elctromagnetic wave propagating vacuum with electric field Ex =
102
sinπ(3x106
z – 9x1014
t) V/m, Ey =0, Ez = 0. Determine the speed, frequency,
wavelength, initial phase and the corresponding magnetic field.
(1st
sem 2007)(4+2marks)
160. Define Poynting vector. Mention its dimension and SI unit. (Supp2004)(3marks)
161. Give the non-mathematical statement of Poynting theorem. (2nd
sem 2006)
162. Starting from Maxwell’s electromagnetic equation in free space, obtain Poynting
theorem. (2nd
sem2005)(7marks)
163. Show that average value of Poynting vector for a plane e-m wave is 2
2
1
HX
ε
µ
.
(2nd
sem 2006)(6marks)
164. Define pointing vector. Mention its dimension.(1st
sem 2009)(2 marks)
165. State and explain Poynting theorem. (1st
sem 2005) (2nd
sem 2004)(4marks)
166. A plane e-m wave propagates horizontally from east to west. If the magnetic field
associated with the wave, at a point in its path, is towards north, what is the direction of
associated electric field at that point? (Supp2006)
167. A plane electromagnetic wave travels vertically upward. If the magnetic field of the
electro magnetic wave is eastward, what is the direction of the associated electric field?
(2nd
sem2005)
168. A plane e-m wave propagates along vertical downward direction. At a given instant, the
direction of E at a point is towards east. What is the direction of B? (1st
sem
2005)(2marks)
169. Explain why e-m wave having frequency less than the plasma frequency cannot
propagate in the corresponding ionized medium. (2nd
sem 2007)(2marks)
170. Define plasma frequency and cut off frequency of an ionized medium. There are
approximately 1011
number of electrons per unit volume in ionosphere. Calculate the
plasma frequency and cut off frequency for the medium. Also calculate the speed of
electromagnetic wave in the same medium having frequency 250 MHz.
(1st
sem 2007)(3+1+1marks)
171. Mention the boundary conditions satisfied by electric field and electric displacement at
the boundary of two media. (Supp2004)(2marks)
172. Mention the boundary conditions satisfied by the vectors E, D, B &H at the interface
between the two non-conducting media. (1st
sem 2003) (1st
sem2004)(4marks)
PROBLEMS

173. In free space electric field intensity is given as E= ŷ 20 cos (ωt-50x) volt/m. Calculate
displacement current density. (2nd
sem 2006)(2marks)
174. Calculate the speed of e-m wave in vacuum. Data given are ε0 = 8.8547x10-12
coulomb2
/
Newton.meter2
and µ0 = 4π x 10-7
Weber/ampere meter (2nd
sem 2006)(2marks)
175. A medium is characterised by relative permittivity εr=45 and relative permeability µr=5.
Calculate the speed of e-m wave in the medium and refractive index of the medium.
(2nd
sem 2006)(2marks)
176. The magnetic vector potential in a given region is a constant vector having magnitude
4πX105
units and points along the positive x-axis. What is the magnitude of the
magnetic induction in the region? (1st
sem 2005)
177. The maximum value of electric field in an electromagnetic wave is 800V/m. Find the
maximum value of magnetic intensity and the average value of pointing vector. (3 mark,2nd
sem 2010)
178. The electromagnetic wave is propagating in free space with electric vector E(z, t)=150
cos(ωt-kz)x. How much average energy is passing through a rectangular hole of length
3 cm and width 1.5 cm or yz or xz plane in one minute time?(2nd
sem 2006)
179. A laser beam from 100watt source is focused on an area of 10-8
m2
. Evaluate the
magnitude of the Poynting vector on the area.(2nd
sem 2004)(2marks)
180. A plane e-m wave propagates in vacuum. The maximum value of electric field is 500
volt/m. Find the average value of Poynting vector for the wave. (Supp2005)(5marks)
181. The amount of electromagnetic energy received by earth in the form of light from sun is
1300 Watt/m2
. Calculate the root mean square value of the electric vector and magnetic
vector of the light wave on the earth surface. (2nd
sem 2007)(4marks)

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