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1,
(a)
In the energy-band diagram of n-type Si, the gap between the bottom of
the conduction band Ec and the donor energy level Ep is of the order of:
(c)
(a)'
(e
10 eV 0-1 eV
(a) (c)
(a)
A steady current flows through a metallic wire whose area of
cross-section (A) increases continuously from one end of the wire to the
other. The magnitude of drift velocity (v) of the free electrons as a function of A' can be shown by :
A
V^
Va
975 nm
SECTION A
(b)
523 nm
t
(b)
Va
An ac source of voltage is connected in series with a p-n junction diode and a load resistor. The correct option for output voltage across load resistance will be:
(£)
(c)
(b)
1eV
(
0-01 eV
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Hydrogen atom initially in the ground state, absorbs a photon which
excites it to n = 5^ level.^ The^ wavelength^ of^ the^ photon^ is^ :
(b)
(d)
DO
V
740 nm
(d)
95 nm
t
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55/1/
In the process^ of^ charging^ of^ a capacitor,^ the^ current^ produced^ between the plates of the capacitor is : (a)
(c)
(a
where symbols have their usual meanings.
(c)
dt
3-0 eV
In an experiment, photons of energy 7-5 eV, are incident on a metal
surface. Electrons emitted from the metal surface are stopped by an
electrode at a potential of - 4-5 V w.r.t. the metal. The work function of the metal is :
7-5 eV
(a) (c)
the coil is :
(b)
(d)
0-12 V 0-19 V
(b)
(a) 8:
(d)
A circular coil of radius 8.0 cm and 40 turns is rotated about its vertical 25
(c) 2:
diameter with an angular speed of (^) Tt rad sl in a uniform horizontal
magnetic field of magnitude 3-0 x 10 T. The maximum emf induced in
1 dog
Ho dt
(b)
1 dog
(d)
dt
4-5 eV 12-0 eV
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Two nuclei have their mass numbers in the ratio of 8 : 1. The ratio of their nuclear densities is :
0-15 V 0-22 V
(b) 4:
(d 1:
P.T.0.
Which of the following pairs of media has the least value of critical
angle? (a) (c)
(a) (e)
(a)
Glass to air
A bar magnet is dropped in a hollow metallic cylinder along its vertical axis. The acceleration of the falling magnet will be :
(b)
Diamond to water
(c) (d)
zero less than g
(a)
RA
(b)
(b)
(d)
The correct graph showing the variation of the resistance (R) of a
cylindrical metal wire as a function of its radius (r), keeping its length
and temperature constant, is : R
(b) (d)
Glass to water Diamond to air
equal to g
Questions number 16 to 18 are Assertion (A) and Reason (R) type questions. Two statements are given one labelled Assertion (A) and the other labelled Reason
(R).Select the correct answer from the codes (a), (0), (c) and (d) as given below.
greater than g
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R
Assertion (A) is true, but Reason (R) is false.
(d)
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation^ of^ the Assertion^ (A).
’r
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct^ explanation^ of^ the Assertion^ (A),
Assertion (A) is false and Reason (R) is also false.
P.T.O.
Assertion (AJ: Photoelectric effect demonstrates the particle nature of
Assertion (A): When a bar of copper is placed in an external magnetic field, the field lines get concentrated inside the bar.
Copper is a paramagnetic substance.
Reason (R):
Reason (R):
light.
Reason (R):
Photoelectric current is proportional to intensity of
incident radiation for frequencies more than the threshold
frequency.
Assertion (A): The phase difference between any two points on a wavefront is zero.
lens?
All points^ on a^ wavefront^ are^ at^ the^ same distance^ from
the source and thusoscillate in the same phase.
The radii of curvature of the faces of a double-convex lens are 20 cm and
30 cm. Its power is 25 D.^ What is the refractive^ index^ of^ the^ glass^ of^ the
SECTION B
6
Briefly explain how the diffusion and drift currents contribute to the formation of potential barrier in a p-n junction diode.
An alpha particle is projected with velocity v (3-0 x 10 mn/s) i into a
region in which magnetic field B = (0-4 T) i + (0-3 T) j) exists.
Calculate the acceleration of the particle in the region. i, jand k are unit vectors along x, y and z axis respectively and charge to mass ratio for alpha^ particle^ is^ 48 x^10 Ckg.
A
The ground state energy of hydrogen atom is -13-6 eV in Bohr model. An
electron makes a transition from an energy level of -1-51 eV to that of -3-4 eV. Calculate the wavelength of the spectral line emitted. Page 13 of 27
2
2
2
2
P.T.0.
(a)
(b)
(a)
(b)
Draw the energy level diagram for hydrogen atom. Mark the transitions corresponding to the series lying in the ultraviolet region, visible region (^) and (^) infrared (^) region.
Three point charges Q, (-15 nC), Q, (10 HC) andQ3 (16 uC) are located at (0 cm, 0 cm), (0 cm, 3 cm) and (4 cm, 3 cm) respectively. Calculate the electrostatic potential energy of this system of charges.
(a)
Draw a diagramn to show the variation of binding energy per
nucleon with mass number for different nuclei and mention its two features. Why do lighter nuclei usually undergo nuclear fusion?
OR
Howdoes the resistance differ from impedance? With the help of a suitable phasor diagram, obtain an expression for impedance of a series LCR circuit, connected to a source v = Vm Sin ot.
Find the condition for resonance in a series LCR circuit connected to a source v =Vm Sin ot, where o can be varied. Give the factors on which the resonant frequency of a series LCR circuit depends. Plot
a graph showing the variation of electric current with frequency in
a series LCR circuit.
A particle is associated with a de Broglie wave of wavelength 1-2 nm. The kinetic energy of the particle is made four times. Caleulate the new value
of the wavelength of the wave.
(i)
OR
(2)
SECTION D
(1) Write two points of difference between an interference pattern and a diffraction pattern. Name any two factors on which the fringe width in a
Young's double-slit experiment depends.
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3
3
3
P.T.O.
(b)
(ii)
(i)
(ii)
In Young's double-slit experiment., the two slits are separated Dy a distance equal to 100 tÉmes the wavelength of light that passes (^) through the (^) slits. (^) Calculate: (2) the angular separation in radians between the central maximum and the adjacent maximum.
(2) the distance between these two maxima on a screen
50 cm from the slits. OR
A spherical surface of radius of curvature R separates two
media of refractive indices ng and n. A point object is placed in front of the surface at distance u in medium of refractive index nj and its image is formed by the surface at distance v,
in the medium of refractive index ng. Derive a relation
between u and v.
A solid glass sphere of radius 6-0 cm has a small air bubble trapped at a distance 3-0 cm from its centre C as shown in the figure. The refractive index of the material of the sphere is 1-5. Find the apparent position of this bubble when seen through the surface of the sphere from an outside point E in air.
E 3 cm
Page 19 of 27
5
5
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- (a)^ ()
(b)
(ii)
(i)
(ii)
State Biot-Savart's law for the magnetic field due to a current carrying element. Use this law to obtain an expression for the magnetic field at the centre of a circular loop of radius 'a' and carrying a^ current^ I.^ Draw^ the^ magnetic^ field^ lines^ for^ a
current loop indicating the direction of magnetic field.
An electron^ is^ revolving^ around the^ nucleus^ in^ a^ circular^ orbit with a speed^ of^ 10'^ ms-l.^ If^ the^ radius^ of^ the^ orbit^ is^10 find the^ current^ constituted^ by^ the^ revolving^ electron^ in^ the orbit.
OR
m,
Derive an^ expression^ for^ the^ force^ acting^ on^ a^ current carrying straight conductor kept^ in^ a^ magnetic^ field.^ State^ the^ rule which is used^ to^ find^ the^ direction^ of^ this^ force.^ Give^ the condition under^ which^ this^ force^ is^ (1)^ maximum,^ and (2) minimum.
Two long parallel straight wires A andB are 2-5 cm apart in air. They carry 5-0 A and 2-5 A currents respectively in opposite directions. Calculate the magnitude of the force exerted by wire A on a 10 cm length of wire B.
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5
5
P.T.0.
The following^ figure^ shows^ a^ circuit^ diagram.^ We^ can^ find^ the^ currents
through and potential differences across different resistors using Kirchhoff's rules.
E =6-0V
r= 102
a
(b)
h
(c)
SECTION E
b
1
Ry= 10Q
OR
What is the current through arm bg?
Answer the following questions based on the above:
(a) Which points are at the same potential in the circuit?
O.Sam
Ry = 50 2
+d
f
e
Page 25 of 27
Rg = 5-0S
(c) Find the potential difference across resistance Rg.
2.5Vot
What is the power dissipated in resistance Ro?
2
2
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