if the threshold wavelength of light for photoelectric ... · if an orbital electron of the...

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

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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.


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


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 =


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


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


The wavelength of the first line in balmer series in

the hydrogen spectrum is l. What is the wavelength

of the second line :


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


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


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


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


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


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


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


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


In semiconductor, which of the following relation

is correct at thermal equilibrium

(A) ni = ne = nn (B) ni2 = nenn

(C) ne = nn = 0 (D)


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


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


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


The combination of NOR gates shown here are

equivalent to

(A) OR (B) AND

(C) NAND (D) XOR


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


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


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.


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 :


Which of the following cannot be emitted by

radioactive substances during their decay?

(A) Protons (B) Neutrinos

(C) Helium nuclei (D) Electrons


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


Which

Thank you 9-8

if the threshold wavelength of light for photoelectric ... · if an orbital electron of the...

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