In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would _____.

(a)

increase by 2 times

(b)

decrease by 2 times

(c)

decrease by 4 times

(d)

increase by 4 times

Two radiations with photon energies 0.9 eV and 3.3 eV respectively are falling on a metallic surface successively. If the work function of the metal is 0.6 eV, then the ratio of maximum speeds of emitted electrons in the two cases will be _____.

(a)

1:4

(b)

1:3

(c)

1:1

(d)

1:9

If the mean wavelength of light from sun is taken as 550 nm and its mean power as 3.8 x 10²⁶ W, then the number of photons emitted per second from the sun is of the order of _____.

(a)

10⁴⁵

(b)

10⁴²

(c)

10⁵⁴

(d)

10⁵¹

The work functions for metals A, B and C are 1.92 eV, 2.0 eV and 5.0 eV respectively. The metal/metals which will emit photoelectrons for a radiation of wavelength 4100 Å is/are _____.

(a)

A only

(b)

both A and B

(c)

all these metals

(d)

none

The work function of a metal is hv₀. Light of frequency v falls on this metal. The photoelectric effect will take place only if ___________.

(a)

v \(\geq\) v₀

(b)

v > 2v_o

(c)

v_o

(d)

v > v_o/2

If the frequency of light in a photo electron experiment is doubled the stopping potential will ______________.

(a)

be doubled

(b)

be halved

(c)

become more than double

(d)

become less than double.

When the intensity of a light source is increased?

(a)

the number of photons emitted by the source in unit time increases

(b)

more energetic photons are emitted

(c)

faster photons are emitted

(d)

total energy of the photons emitted per unit time decreases.

Stopping potential of emitted photo electrons is given by (where ф = hv₀) _____________.

(a)

\(\frac { hv-{ \phi }_{ 0 } }{ e } \)

(b)

hv-ф

(c)

\(\frac { hv }{ e } \)

(d)

\(\frac { hv+{ \phi }_{ 0 } }{ e } \)

An electron of mass 'm' and charge 'e' accelerated from rest through a potential of V volt then its final velocity is ______________.

(a)

\(\sqrt { \frac { { V }_{ e } }{ m } } \)

(b)

\(\sqrt { \frac { { V }_{ e } }{ 2m } } \)

(c)

\(\sqrt { \frac { { 2V }_{ e } }{ m } } \)

(d)

\(\sqrt { \frac { { 2V }_{ a } }{ m } } \)

Louis de Broglie proposed the theory of _________

(a)

waves

(b)

matter waves

(c)

matter corpuscles

(d)

secondary wavelets

At the stopping potential, photoelectric current is _______

(a)

maximum

(b)

a constant

(c)

zero

(d)

infinity

______ theory of light was proposed by Maxwell

(a)

Electromagnetic

(b)

Corpuscular

(c)

Wave

(d)

Quantum

The energy spent in releasing a photoelectron is called photoelectric _______ of the metal.

(a)

energy

(b)

ionization potential

(c)

work function

(d)

absorption energy

The cathode is coated with a material of low work function because ________

(a)

a large number of photo-electrons can be got

(b)

high work function should be achieved later

(c)

it is transparent

(d)

it is low in cost

Calculate the momentum of the particle of mass = 2g and velocity = 5.2 cm/s.

(a)

10.58 kgm/s

(b)

10.4 g cm/s

(c)

5.2 g cm/s

(d)

4.10 kgm/s

de- Broglie's concept confirms _______ postulate.

(a)

Bohr's

(b)

Newton's

(c)

Sommerfeld

(d)

Huygen's

Electron microscope employ magnetic lenses of _______ focal lengths to obtain large magnification.

(a)

short

(b)

long

(c)

infinite

(d)

zero

_______ is the only disadvantage of electron microscopes.

(a)

Operation only in high vacuum

(b)

Small size

(c)

High magnification

(d)

Cost

In Newtonian mechanics, mass, time, length and space were treated as ________

(a)

relative

(b)

absolute

(c)

variables

(d)

infinity

In classical mechanics, the time interval between two events has _______ value(s) for any two observers in motion.

(a)

different

(b)

zero

(c)

variable

(d)

same