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In the photoelectric effect the velocity of ejected electrons depends upon the nature of the target and

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Important Questions on Dual Nature of Matter and Radiation

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>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]

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

A photoelectric surface is illuminated successively by monochromatic light of wavelength

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 of the material is:
(

h

= Planck's constant,

c

= speed of light)

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>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>Dual Nature of Matter and Radiation>Photoelectric Effect

In a photoelectric experiment, a parallel beam of monochromatic light with the power of

200 W

is incident on a perfectly absorbing cathode of work function

6.25 eV

. The frequency of light is just above the threshold frequency so that the photoelectrons are emitted with negligible kinetic energy. Assume that the photoelectron emission efficiency is 100%. A potential difference of

500 V

is applied between the cathode and the anode. All the emitted electrons are incident normally on the anode and are absorbed. The anode experiences a force

F = n \times 10^{- 4} N

due to the impact of the electrons. The value of

n

is __________. Mass of the electron

m_{e} = 9 \times 10^{- 31} kg a n d 1.0 eV = 1.6 \times 10^{- 19} J

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

Among the following photosensitive substances, the one which emits electrons when it is illuminated by visible light is

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>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>Dual Nature of Matter and Radiation>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:

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

Maximum kinetic energy of a photoelectric varies with the frequency

(f)

of the incident radiation as

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

A beam of photons with an energy of

10.5 eV

strike a metal plate. The photoelectrons are emitted with maximum velocity of

1.6 \times 10^{6} m s^{- 1}

. The work function of the metal is
(Assume mass of electron

= 9 \times 10^{- 31} kg

and Charge of electron

= 1.6 \times 10^{- 19} C

)

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

The radiation corresponding to

3 \to 2

transition of a hydrogen atom falls on a gold surface to generate photoelectrons. These electrons are passed through a magnetic field of

5 \times 10^{- 4} T

. Assume that the radius of the largest circular path followed by these electrons is

7 mm

, the work function of the metal is:
(Mass of electron

= 9.1 \times 10^{- 31} kg

)

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>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:

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

When photon of energy

4.0 e V

strikes the surface of a metal

A,

the ejected photoelectrons have maximum kinetic energy

T_{A} e V

and de-Broglie wavelength

λ_{A} .

The maximum kinetic energy of photoelectrons liberated from another metal

B

by photon of energy

4.50 e V

T_{B} = (T_{A} - 1.5) e V .

If the de-Broglie wavelength of these photoelectrons

λ_{B} = 2 λ_{A},

then the work function of metal

B

is:

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>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 :

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

When a certain photosensitive surface is illuminated with a monochromatic light of frequency

ν,

the stopping potential of the photo current is

- \frac{V_{0}}{2} .

When the surface is illuminated by monochromatic light of frequency

\frac{ν}{2},

the stopping potential is

- V_{0} .

The threshold frequency for photoelectric emission is

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>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>Dual Nature of Matter and Radiation>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>Dual Nature of Matter and Radiation>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>Dual Nature of Matter and Radiation>Photoelectric Effect

Which of these statements is true regarding photoelectric emission?

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photoelectric Effect

Radiation, with wavelength

6561 Å

falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of

3 \times 10^{- 4} T

. If the radius of the largest circular path followed by the electrons is

10 m m

, the work function of the metal is close to:

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>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

In the photoelectric effect the velocity of ejected electrons depends upon the nature of the target and

Important Questions on Dual Nature of Matter and Radiation

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