If the threshold wavelength of light for photoelectric
effect from sodium surface is 6800 Aº then,
the work function of sodium is
(A) 1.8 eV (B) 2.9 eV
(C) 1.1 eV (D) 4.7 eV
MENTI QUIZ - 7
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
In photoelectric effect, we assume the photon energy is proportional to
its frequency and is completely absorbed by the electrons in the metal.
Then the photoelectric current (u > nth)
(A) Decreases when the frequency of the incident photon
increases.
(B) Increases when the frequency of the incident photon
increases.
(C) Does not depend on the photon frequency but only on the
intensity of the incident beam.
(D) Depends both on the intensity and frequency of the incident beam.
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
If the frequency of light in a photoelectric experiment
is doubled then stopping potential will
(A) be doubled
(B) be halved
(C) become more than double
(D) become less than double
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Two particles have identical charges. If they are
accelerated through identical potential differences,
then the ratio of their deBroglie wavelength would be
(A) l1 : l2 = 1 : 1 (B) 1 : l2 = m2 : m1
(C) l1 : l2 = (D) l1 : l2 =
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
12 m:m 21 m:m
Which energy state of doubly ionized lithium
(Li++) has the same energy as that of the ground
state of hydrogen ? Given Z for lithium = 3 :
(A) n = 1 (B) n = 2
(C) n = 3 (D) n = 4
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
If an orbital electron of the hydrogen atom jumps
from the ground state to a higher energy state, its
orbital speed reduces to half its initial value. If the
radius of the electron orbit in the ground state is r,
then the radius of the new orbit would be :
(A) 2r (B) 4r
(C) 8r (D) 16r
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
The wavelength of the first line in balmer series in
the hydrogen spectrum is l. What is the wavelength
of the second line :
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
The energy of the reaction Li7 + p ¾ 2 He4 is (the
binding energy per nucleon in Li7 and He4 nuclei are
5.60 and 7.06 MeV respectively.)
(A) 17.3 MeV
(B) 1.73 MeV
(C) 1.46 MeV
(D) depends on binding energy of proton
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
10 grams of 57Co kept in an open container decays b–
particle with a half-life of 270 days. The weight of the
material inside the container after 540 days will be
very nearly -
(A) 10 g (B)7.5 g
(C) 5 g (D)2.5 g
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
92U235 nucleus absorbs a slow neutron and undergoes
fission into 54X139 and 38Sr94 nuclei. The other
particles porduced in this fission process are
(A) 1 b and 1 a
(B) 2 b and 1 neutron
(C) 2 neturons
(C) 3 neutrons
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
The binding energies of two nuclei Pn and Q2n and x
and y joules. If 2x > y then the energy released in the
reaction
Pn + Pn Q2n, will be
(A) 2x + y (2) 2x – y
(C) –(2x – y) (D) x + y
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
If N0 is the original mass of the substance of half-
life period tl/2 = 5 years, then the amount of
substance left after 15 years is :
(A) N0 / 8 (B) N0 / 16
(C) N0 / 2 (D) N0 / 4
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
A nucleus with Z = 92 emits the following in a
sequence : a, a, b–, b–, a, a, a, a; b–, b–, a, b+,
b+, a. The Z of the resulting nucleus is :
(A) 76 (B) 78
(C) 82 (D) 74
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
An n-type semi-conductor has donor levels at 500
meV above the valence band, the frequency of
light required to create a hole is nearly
(A) 8 × 1013 Hz (B) 12 × 1013 Hz
(C) 22 × 1013 Hz (D) 15 × 1013 Hz
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
A diode can convert
(A) A.C. into D.C. but not D.C. into A.C.
(B) D.C. into A.C. but not A.C. into D.C.
(C) A.C. into D.C. and D.C. into A.C.
(D) All of these
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
In semiconductor, which of the following relation
is correct at thermal equilibrium
(A) ni = ne = nn (B) ni2 = nenn
(C) ne = nn = 0 (D)
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
n
ei
n
nn
If the current amplification factor for a transistor
connected in common emitter configuration is 100 and
input resistance is 200 W, then calculate the power gain
(A) 4 × 104
(B) 5 × 103
(C) 7 × 103
(D) 45 × 104
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
BC
ERB
800 W
8V
RL0.8V
–+
–+
Choose the correct statement from following
(A) p-type semiconductor is positively charged
(B) Phosphor is acceptor type impurity
(C) Donor atom electrons have energy state that is
slightly below the lowest energy state of
CB(Conduction Band)
(D) None of thesewww.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Reading of Ammeter in following circuit
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
A
5 V
4 W
6 W
3 W
‘A +AB’Boolean equation is equal to
(A) A (B) B
(C) A + B (D) AB
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
The combination of NOR gates shown here are
equivalent to
(A) OR (B) AND
(C) NAND (D) XOR
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Y
A
B
In the given circuit diode is ideal. The potential
difference across 2 W resistance is
(A) 10 V (B) 8 V
(C) 20 V (D) Zero
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
20 V
3 W
2 W
Which of the following is a wrong description of binding energy
of a nucleus ?
(A) It is the energy required to break a nucleus into its
constituent nucleons.
(B) It is the energy released when free nucleons combine to
from a nucleus
(C) It is the sum of the rest mass energies of its nucleons minus
the rest mass energy of the nucleus
(D) It is the sum of the kinetic energy of all the nucleons in
the nucleuswww.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
A freshly prepared radiocative source of half-life 2 h
emits radiation of intensity which is 64 times the
permissible safe level. The minimum time after
which it would be possible to work safely with this
source is -
(A) 6 h (B) 12 h
(C) 24 h (D) 128 hwww.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
The half life of thorium (Th232) is 1.4 × 1010
years. Then the fraction of thorium atoms
decaying per year is very nearly -
(A) 1 × 10–11 (B) 4.95 × 10–11
(C) 0.69 × 10–11 (D) 7.14 × 10–11
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Fusion reaction is possible at high temperature
because -
(A) atoms are ionised at high temperature
(B) molecules break-up at high temperature
(C) nuclei break-up at high temperature
(D) kinetic energy is high enough to overcome
repulsion between nuclei.
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Half-lives of two radioacitve substances A and B
are respectively 20 min and 40 min. Initially the
samples of A and B have equal number of nuclei.
After 80 min the ratio of remaining number of A
and B nuclei is :
(A) 1 : 16 (B) 4 : 1
(C) 1 : 4 (D) 1 : 1www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
When U238 nucleus originally at rest, decays by
emitting an alpha particle having a speed u, the recoil
speed of the residual nucleus is :
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Which of the following cannot be emitted by
radioactive substances during their decay?
(A) Protons (B) Neutrinos
(C) Helium nuclei (D) Electrons
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
If the binding energy of the electron in a
hydrogen atom is 13.6 eV, the energy required to
remove the electron from the first excited state
of is
(A) 122.4 eV (B) 30.6 eV
(C) 13.6 eV (D) 3.4 eV
www.gangwarinstitue.com Contact : 8400-582-582, 8604-582-582
Which
Thank you 9-8