Trial
Examination 2010
Subject –Physics XII
Gaselo HSS
(This paper contains
7 printed pages)
This paper is divided into two parts. Part I is compulsory and in Part
II answer any 4 questions from section A, 3 questions from section B, and 2
Questions from section C. Paper is for the duration of Three hours and is out
of 100 marks.
Part I (Answer all questions) 40 Marks
Question 1
A. Multiple-choice Questions (1´10=10 Marks)
i.
Which of the
following phenomena cannot take place in sound waves?
a)
reflection
b)
interference
c)
diffraction
d)
polarization.
ii.
The depletion layer in the p-n junction is formed by:
a)
diffusion of charge carriers
b)
drift of electrons
c)
drift of holes
d)
migration of impurity ions.
iii) In a X-ray tube, the
quality of the emitted X-ray beam controlled by:
a)
increasing the filament current
b)
decreasing the filament current
c)
increasing the potential difference across the ends of the tube
d)
decreasing the potential difference across the ends of the tube.
iv) How many lines of force
start from a unit charge?
a)
of force
of force
b)
of force
of force
c)
of force
of force
d)
of force
of force
v) The time period of oscillation of a freely suspended magnet doesnot
depend upon:
a) the length of the magnet
b) the pole strength of the magnet
a)
the horizontal component of the earth’s magnetic field
a)
the nature of the material of suspension
vi) The refractive index of a glass prism depends upon:
a) the angle of prism
b) the angle of
devaition of light ray
c) the colour of
incident light
d) the intensity of
incident light.
vii) The magnifying power of of an astronomical telescope at normal
adjustment is :
a) fofe
b) fe /
fo
c) fo /
fe
d) fofe
/ (fo+fe)
viii) A photon of wavelength can be associated to have a mass equal to:
b)
zero
c)
h/cl
c) hl/c
b)
hc/l
ix) Though quantum theory of
light can explain a number of phenomenon observed with light it is necessary to
retain the wave nature of light to explain the phenomenon of
a)
photo electric effect
b)
diffraction
c)
Compton effect
d)
black body radiation.
x) Which doesnot represent the unit of power :
a) J/s
d)
AV
e)
f)
B. Match the following (1/2´8 = 4marks)
Fill in gaps in the right hand column with the best answer the matches
the column A from Column B. First one is done for you as an example.
Column A Column
B Answer
E.g. 9. control rods c)
nuclear reactor
1.Biot-Savart
Law a)
Bohr’s model -----2.Characteristics curves b) fission reaction -----------
3.Orbital motion of
an c) nuclear reactor electron is quantised d)fusion
reaction -------------
4. Thermopile e)
Transistors ------------
5. Tangent law f) Refraction
of light------------ 6.wheatstone
bridge g)
null point
7. Simple microscope h) moving coil galvanometer -------
8. Neutral point i) object
within focus------------
9. control rods j) Magnetic
Field ------------
k)
Magnetic induction-------------
l)
Characteristics curves
C. Fill in the blanks (1/2´12=6 marks)
i)
The base of a transistor is ----------------and -------------doped,
compared to the emitter and the collector. (thick, thin, lightly, heavily)
ii)
To convert a galvanometer into a voltmeter a ------------resistance is
connected ------------------- while to convert into an ammeter a
------------------ resistance is connected in ------------. ( high, low, in
series, in parallel)
iii)
Atoms having same--------------but different -------------are called
isotopes. (atomic number, mass number, wave number, Avagrado number)
iv)
De-Broglie predicted the dual nature of matter and derieved a relation
between the ----------- of matter and the -----------(frequency, wavelength,
intensity, momentum).
v)
The magnetic substances having negative magnetic susceptibility are
called -------------and those having positive susceptibility are
called------------( dia, para, ferro, non magnetic)
D. Write down whether the following
statements are True or False and rewrite the sentence in correct form if they
are false.. (1´4 = 4Marks)
i)
The resistance of graphite and
non-metals increases with rise in temperature.
ii)
In equation given m represents the
magnetic Susceptibility
m=1+4pk
iii)
Right-angled prisms are preferred over the reflecting mirrors while
constructing a periscope.
iv)
When a photon falls on a metal surface it transmit whole of its energy
‘hn’ to anyone of the
electrons present in the metal surface.
E. Short questions (2´7+1´2= 16 Marks)
i)
The half-life period of a radioactive material is 16 hours. After how
much time will 6.25% of the material remains undecayed.
ii)
What is the force acting between two parallel current carrying wires,
current flowing in the same direction. Mention the direction of force between
the two parallel wires.
iii)
What are the conditions necessary for two sources of light to produce
interference patterns?
iv)
A current of 2A flowing through a coil of 100 turns gives rise to a
magnetic flux of 
Wb/turn. Calculate the magnetic energy associated with the
coil?
Wb/turn. Calculate the magnetic energy associated with the
coil?
v)
Mention any two factors on which temperature of inversion of a
thermocouple depends.
vi)
Calculate de-Broglie’s wavelength of an electron beam accelerated
through a potential difference of 60 volts.
vii)
Draw a ray diagram to show how the image is magnified in the simple
microscope?
viii)
Calculate the momentum p and energy E of a photon of wavelength equals
to 331.5 nanometer.
ix)
Write down the expression for Biot- Savart law in the vector form.
x)
How is the emitter circuit and collector circuits biased in the
transistors?
Part II (60 Marks)Section A
Answer 4 Questions
from this section.(7x4= 28 Marks)
Question 2
a)
Derive an
expression for the electric potential at a point due to a point charge. [3
marks]
b)
An electric
lamp has 20 capacitors each of capacitance 5 microfarad connected in parallel.
The lamp is operated at 100 volts. Calculate how much energy is radiated in a
flash. [4
marks]
Question 3
a)
What is
See-back effect? Show with the help of a diagram how is the thermo-emf of
thermo-couple measured.
[3 marks]
b)
Draw a
labelled diagram showing an electric dipole making an angle q with uniform electric field E. Derive an
expression for the torque experienced by the dipole. [4marks]
c)
Question 4
a) What is relative permeability of a magnetic
material? How is it related to the
magnetic susceptibility? How does permeability help us in classifying dia, para and Ferro magnetic materials? [3Marks]
b) The
resistance of a galvanometer is 10ohm. It can measure a maximum current of I A.
Giving necessary calculations, explain with the help of a diagram, how this
galvanometer can be converted into a voltmeter reading upto 100 volt. [3
marks]
Question 5
a)
A wheat stone bridge is made of four resistors R1, R2, R3 and
R4. Obtain the relation between these resistors when the bridge is
balanced. (4 marks)
b)
Define
Joules law. Explain how Law of resistance can be verified.
Question 6
a) A pure inductance of 1.0 H is connected
across an 110V, 70 Hz source.
Find i) Reactance
ii) Current
iii) Peak value of current. [3 marks]
b) A
100mF capacitor is charged to a potential
difference of 100 volts. The energy stored in the capacitor is made to
discharge through the flash lamp of a camera in 0.1 milli-seconds giving a
powerful flash. Calculate how much energy will be radiated in the flash and the
power of the flash. (4)
Question 7
a) A
step up transformer operates on a 220V supply and supplies a load of 5A. The
ratio of primary and secondary coil is 1:20. Calculate
i) the
p.d. across the secondary coil.
ii) the current into primary and
iii) the power output.
b) State and explain Kirchoff’s law for the
electrical circuits.
Section B Answer any three questions from this section.(6´3=18 Marks)
Question 8
a)
State Huygens’
Principle. Using this principle illustrate the different types of wave fronts
formed. (3)
b)
Two coherent
sources are placed 0.12mm apart and the fringes are observed on a screen 70cm
far. It is found that with a source of monochromatic light, the 4th
bright fringe is found at a distance of 10.5mm from the central fringe. Find
the wavelength of light. (3)
Question 9
a) What are the components of the complete
electro-magnetic spectrum? Name two components whose frequencies are more than
that of violet light and two whose frequencies are less than red light. What are
the characteristic features of the electric and magnetic fields associated with
the electro-magnetic waves? (4)
b) Explain the term critical angle. If the
refractive index of diamond with respect to air is 2.42, find the critical
angle of diamond. (2)
Question 10
a) What is a Polaroid? How is it used to obtain
plane-polarized light from ordinary light? If the polarizing angle for air
glass interface is 56.30, what is the angle of refraction in glass? (3)
b) Give the theory and the method for the
determination of the speed of light by Michel son’s method. (3)
Question 11
c)
Draw a graph
showing the variation of intensity on the screen of a single slit diffraction
grating when a monochromatic light illuminates the slit. Explain why there are
dark bands on either side of central maxima. (2)
d)
Draw a ray
diagram for an astronomical telescope when it is adjusted for normal vision. [2]
c) Explain
the term critical angle. If the refractive index of diamond with respect to air
is 2.42, find the critical angle of diamond. (2)
Question 12.
a) What is spherical
aberration? Discuss one method to remove this aberration. (2)
b)
Derive the relation to calculate the dispersive power when white light
is made to pass through a prism. (2)
c)
What is
meant by pure and impure Spectrum? Draw a diagram of a spectrometer and
describe its parts.[2]
Section C
(Answer any TWO questions)
[2
´ 7 = 14 marks]
Question 13
a)
Explain how
Rutherford model of the atom failed to explain the existence of sharp lines in
the hydrogen spectrum. How did Bohr remove this difficulty? (3)
b)
Draw a properly
labeled diagram of a modern X-ray tube and describe how X-rays are produced in
it. State briefly how i) the intensity and ii) the penetrating power of X-rays
are controlled. (2)
c)
What do you
understand by ‘nuclear binding energy’? Explain how this energy is given out in
the case of nuclear fission and nuclear fusion. (2)
Question 14
a)
How p-n
junction diode act as a full wave rectifier. Explain its working with a
suitable diagram. (3)
b)
Describe
de-Broglie’s concept of matter waves and obtain the expression for the momentum
and wavelength of the particle. (2)
c)
Draw the
symbol for the logic gate NAND. Write its truth table and Boolean equations. (2)
Question 15
a)
What is
Compton scattering? State briefly its importance.[2]
b) The
ground energy level and two higher energy levels of hydrogen are respectively
–13.6 eV and –1.5 eV. Calculate the energies corresponding to the spectral
lines produced by transition among these levels. Show the transition with the
help of energy–level diagram. (2)
c) Describe the main features of the nuclear
reactor? What are functions of the
coolant and a moderator in it? Write any two uses of a nuclear reactor. (3)
PHYSICAL CONSTANTS
h = 6.63´10-34 J.s
me = 9.1´10-31 kg
e = 1.6´10-19 C
1eV = 1.6´10-19 J
= 9.0´109 SI units
c = 3.00´108 m/s
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