If the work function of two metals X and Y are 4 . 17 eV and 8 . 24 × 10 - 19 J respectively, then for which metal lesser amount of energy is required to emit electron?

Given the work function of the metal X = 4 . 17 eV . The work function of metal Y = 8 . 24 × 10 - 19 J = 8 . 24 × 10 - 19 1 . 6 × 10 - 19 = 5 . 15 eV . The minimum amount of energy required by an electron to just escape from the metal surface is called the work function of the metal. It is clear that the metal X has a lower work function hence it requires less amount of energy to eject electrons from its surface.

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The metal which has the highest work function in the following is

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Important Questions on Dual Nature of Radiation and Matter

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

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)

MEDIUM

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

Which of these statements is true regarding photoelectric emission?

EASY

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

If the work function of two metals

X and Y

are

4.17 eV and 8.24 \times 10^{- 19} J

respectively, then for which metal lesser amount of energy is required to emit electron?

EASY

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

What is thermionic emission?

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

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 Radiation and Matter>Electron Emission

When light of wavelengths

400 nm

and

500 nm

are allowed to fall on the cathode surface of a photocell, the stopping potentials of

1.2 V

and

0.57 V

respectively are required to stop photoelectric current. Calculate the Planck's constant.

MEDIUM

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

If the light of wavelength $412.5 nm$ is incident on each of the metals given below, which ones will show photoelectric emission and why?

Metal	Work Function(eV)
Na	1.92 eV
K	2.15 eV
Ca	3.20 eV
Mo	4.17 eV

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

When green light is incident on a certain metal surface, electrons are emitted but no electrons are emitted by yellow light. If red light is incident on the same metal surface

MEDIUM

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

What is photoelectric effect?

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

What is work function?

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

The surface of metal is illuminated with the light of

400 nm

. The kinetic energy of the ejected photoelectrons was found to be

1.68 eV

. The work function of the metal is

(hc = 1240 eV nm)

HARD

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

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:

EASY

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

Mention any one type of electron emission.

MEDIUM

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

The work function for a metal surface is $2.2 eV$ . If light of wavelength $5000 \overset{0}{A}$ is incident on the surface of the metal, find the threshold frequency and incident frequency. Will there be an emission of photoelectrons or not?

$(c = 3 \times 10^{8} m s^{- 1}, 1 eV = 1.6 \times 10^{- 19} J, h = 6.63 \times 10^{- 34} Js)$

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

What is photoelectric effect? Frame Einstein's photoelectric equation. Discuss how it gives the concept of threshold frequency.

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

The time lag between a photon hitting the surface of a metal and the emission of a photoelectron is

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

The work function of Platinum is twice that of Calcium. If the minimum photon energy required to emit photoelectrons from the surface of Platinum is

E,

then for Calcium, the minimum photon energy would be

MEDIUM

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

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

)

HARD

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

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 Radiation and Matter>Electron Emission

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

The metal which has the highest work function in the following is

Important Questions on Dual Nature of Radiation and Matter

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