Guru Harkrishan Public School, Vasant Vihar
PRE MOCK EXAMINATION-2014-2015
SUB. : PHYSICS.
M.M - 50.
CLASS-XII.
TIME - 2 Hours
GENERAL INSTRUCTIONS:
(a)
All questions are compulsory.
(b) Questions 1 to 4 carry 1mark each.
(c)
Questions 5 to 10 carry 2 marks each.
(d) Questions 11 to 18 carry 3 marks each.
(e)
Questions 19 to 20 carry 5 marks each.
1.
Define Transducer for a communication system.
2.
What is the de Broglie wavelength associated with an electron,
through a potential difference of 100 volts ?
3
What is the polarising angle of a medium of refractive index
4.
Arrange radioactive radiations α rays, βrays, γrays
order of their penetrating power.
5.
A message signal of frequency 10 kHz and peak voltage of 10 volts is used to
modulate a carrier of frequency 1MHz and peak voltage of 20 volts .
Determine : (a) Modulation index (b) The side bands produced .
6.
Define stopping potential . Does the stopping potential in photoelectric
emission depend upon.
(i) the intensity of the incident radiation?
(ii) the frequency of the incident radiation ?
7.
Using Huyghen's principle show that for a parallel beam incident on a
reflecting surface that angle of reflection is equal to angle of incidence .
8.
An electron and a photon each have a wavelength 2 nm. Find
(i) their momenta,
(ii) the energy of the photon.
9.
(a)
(b)
10.
If the output of a 2-input NAND gate is fed as the input to a NOT gate, name
the new gate obtained and write down its truth table.
accelerated
3 ?
in the increasing
Name the principle on which solar cell works.
Name the material which is preferred for making LED.
11.
State the essential condition for diffraction of light to take place. Write
expressions for the conditions of maxima and minima observed in the
diffraction pattern due to single slit. Draw a graph showing the variation of the
intensity with angle in single slit experiment. Also write one feature which
distinguishes the observed pattern from the double slit interference pattern.
12.
(a)
In a radioactive decay, a nucleus emits an alpha particle and two beta
particles successively. Show that the final nucleus is an isotope of the
original nucleus with the help of equation.
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13.
14.
(b)
A radioactive isotope has a half life of T years. After how much time is
its activity reduced to 6.25% of its original activity?
(a)
(b)
Draw a detailed block diagram of a communication system.
A TV tower is 80 m tall. Calculate the maximum distance up to which
the signal transmitted from the tower can be received. Take R=6400 km.
Calculate the binding energy of an alpha particle in MeV. Given
mass of proton = 1.007825 amu.
mass of neutron = 1.008665 amu.
mass of He nucleus = 4.002800 amu
Take 1amu = 931 MeV.
15.
What is amplitude modulation? Derive an expression of amplitude modulated
wave . Discuss the frequency spectrum of amplitude modulated signal with its
diagram.
16.
Write Einstein’s photoelectric equation .Draw a graph between the frequency
of incident radiation and the maximum kinetic energy of the electrons
emitted from the surface of a photosensitive material. State clearly how this
graph can be used to determine Planck’s constant and work function of the
material.
17.
Explain, with the help of a circuit diagram ,the use of p-n junction diode as
full wave rectifier. Draw input and output voltages graphically.
18.
Using Bohr’s postulates, derive an expression for the radii of the permitted
orbits in the Hydrogen atom. Also obtain an expression for the total energy of
an electron in the nth orbit of an atom.
19.
With the help of a circuit diagram explain the working of transistor as a
common emitter amplifier .Show input and output voltages graphically .Also
write the expression for current gain, voltage gain and power gain.
20.
Obtain the mathematical expression for the fringe width in YDSE with the
help of suitable diagram. Yellow light of wavelength 6000Å produces fringes
of width 0.8 mm in YDSE. What will be the fringe width if the light source is
replaced by another monochromatic source of wavelength 7500Å and the
separation between the slits is doubled?
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