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Stopping potential in the experimental setup shown in the figure is

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Important Questions on Photoelectric Emission and Production and Properties of X-rays

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Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

In a historical experiment to determine Planck's constant, a metal surface was irradiated with light of different wavelengths. The emitted photoelectron energies were measured by applying a stopping potential. The relevant data for the wavelength

(λ)

of incident light and the corresponding stopping potential

(V_{0})

are given below:

$λ (μ m)$	$V_{0} (v o l t)$
0.3	2.0
0.4	1.0
0.5	0.4

Given that

c = 3 \times 10^{8} m s^{- 1} and e = 1.6 \times 10^{- 19} C,

Planck's constant (in units of

J s

) found from such an experiment is :

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A metal plate of area

1 \times 10^{- 4} m^{2}

is illuminated by a radiation of intensity

16 mW m^{- 2}

. The work function of the metal is

5 eV .

The energy of the incident photons is

10 eV

and only

10 %

of it produces photo electrons. The number of emitted photo electron per second and their maximum energy, respectively, will be:

[1 eV = 1.6 \times 10^{- 19} J]

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The maximum velocity of the photoelectrons emitted from the surface is

v

when light of frequency

n

falls on a metal surface. If the incident frequency is increased to

3 n

, the maximum velocity of the ejected photoelectrons will be:

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

When a metallic surface is illuminated with radiation of wavelength

λ

, the stopping potential is

V

. If the same surface is illuminated with radiation of wavelength

2 λ

, the stopping potential is

\frac{V}{4}

. The threshold wavelength for the metallic surface is:

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The radiation corresponding to

3 \to 2

transition of hydrogen atom falls on a metal surface to produce photoelectrons. These electrons are made to enter a magnetic field of

3 \times 1 0^{- 4} T

. If the radius of the largest circular path followed by these electrons is 10.0 mm, the work function of the metal is close to :

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Radiation of wavelength

λ

is incident on a photocell. The fastest emitted photoelectron has a speed

v

. If the wavelength is changed to

\frac{3 λ}{4}

, the speed of the fastest emitted photoelectron will be

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

On a photosensitive material, when the frequency of incident radiation is increased by

30 %

, the kinetic energy of emitted photoelectrons increases from

0.4 eV

0.9 eV

. The work function of the surface is

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A photoelectric material having work-function

ϕ_{0}

is illuminated with a light of wavelength

λ (λ < \frac{h c}{ϕ_{0}})

. The fastest photoelectron has a de Broglie wavelength

λ_{d}

. A change in wavelength of the incident light by

Δ λ

results in a change

Δ λ_{d}

λ_{d}

. The ratio

\frac{Δ λ_{d}}{Δ λ}

is proportional to

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The magnetic field associated with a light wave is given, at the origin, by

B = B_{0} [\sin (3.14 \times 10^{7}) c t + \sin (6.28 \times 10^{7}) c t] .

If this light falls on a silver plate having a work function of

4 .7 eV,

what will be the maximum kinetic energy of the photoelectrons?

(c = 3 \times 10^{8} m s^{- 1}, h = 6 .6 \times 10^{- 34} J s)

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

When a certain metallic surface is illuminated with monochromatic light of wavelength

λ,

the stopping potential for photoelectric current is

3 V_{0}

and when the same surface is illuminated with light of wavelength

2 λ,

the stopping potential is

V_{0} .

The threshold wavelength of this surface for photoelectric effect is

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A metal surface is illuminated by light of two different wavelengths 248 nm and 310 nm. The maximum speeds of the photoelectrons corresponding to these wavelengths are u₁ and u₂, respectively. If the ratio

u_{1} : u_{2} = 2 : 1

and

h c = 1240 eV nm

, the work function of the metal is nearly

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Light of wavelength $λ_{p h}$ falls on a cathode plate inside a vacuum tube as shown in the figure. The work function of the cathode surface is $ϕ$ and the anode is a wire mesh of conducting material kept at a distance $d$ from the cathode. A potential difference $V$ is maintained between the electrodes. If the minimum de Broglie wavelength of the electrons passing through the anode is $λ_{e},$ which of the following statement(s) is(are) true ?
Question Image

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

When photons of wavelength

λ_{1}

are incident on an isolated sphere, the corresponding stopping potential is found to be

V

. When photons of wavelength

λ_{2}

are used, the corresponding stopping potential was thrice that of the above value. If light of wavelength

λ_{3}

is used then find the stopping potential for this case:

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The photoelectric threshold wavelength of silver is

3250 \times 10^{- 10} m

. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength

2536 \times 10^{- 10} m

is:-

(G i v e n h = 4.14 \times 10^{- 15} eV s a n d c = 3 \times 10^{8} m s^{- 1})

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A photoelectric surface is illuminated successively by monochromatic light of wavelengths

λ and \frac{λ}{2} .

If the maximum kinetic energy of the emitted photoelectrons in the second case is

3

times that in the first case, the work function of the surface is :

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The stopping potential $V_{o}$ (in volt) as a function of frequency $(v)$ for a sodium emitter, is shown in the figure. The work function of sodium, form the data plotted in the figure, will be:
(Given: Planck’s constant $h = 6.63 \times 10^{- 34} J s$ , electron charge $e = 1.6 \times 10^{- 19} C)$
Question Image

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A beam of electromagnetic radiation of intensity

6.4 \times 10^{- 5} W {cm}^{- 2}

is comprised of wavelength,

λ = 310 n m

. It falls normally on a metal (work function

ϕ = 2 eV

) of surface area of

1 {c m}^{2}

. If one in

10^{3}

photons ejects an electron, total number of electrons ejected in

1 s

10^{x}

(h c = 1240 e V n m, 1 e V = 1.6 \times 10^{- 19} J),

then

x

is ___________

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Photons with energy of

5 eV

are incident on a cathode,

C

in a photoelectric cell. The maximum energy of emitted photoelectrons is

2 eV.

When photons of energy

6 eV

are incident on

C

, no photoelectrons will reach the anode,

A

, if, the stopping potential of

A

relative to

C

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The anode voltage of a photocell is kept fixed. The wavelength

λ

of the light falling on the cathode is gradually changed. The plate current

I

of the photocell varies as follows :

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Light of wavelength

500 nm

is incident on a metal with work function

2.28 eV

. The de Broglie wavelength of the emitted electron is:

Stopping potential in the experimental setup shown in the figure is

Important Questions on Photoelectric Emission and Production and Properties of X-rays

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