EASY

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The phenomenon of electron emission is defined as the emission of electrons from the surface that is caused by a change in temperature, radiation, or a strong electric field.

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Important Questions on Thermionic Emission and Radioactivity

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

If the two metals

A

and

B

are exposed to radiation of wavelength

350 nm

. The work functions of metals

A

and

B

are

4.8 eV and 2.2 eV

. Then choose the correct option

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Which of those metal having least work function

(ϕ_{0})

among them?

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

The light emitted in the transition

n = 3

n = 2

(where

n

is the principal quantum number of the state) in hydrogen is called

H_{α}

-light. Find the maximum work function that a metal can have so that

H_{α}

-light can emit photoelectrons from it.

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

)

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

HARD

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : The photoelectric effect does not take place, if the energy of the incident radiation is less than the work function of a metal.

Reason R : Kinetic energy of the photoelectrons is zero, if the energy of the incident radiation is equal to the work function of a metal.

MEDIUM

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

MEDIUM

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

)

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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:

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

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

Science>Physics>Thermionic Emission and Radioactivity>Work Function

The experimental set up to produce thermionic electron emission can be cathode ray tube.

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

State the characteristics required for a good thermionic emitter.

MEDIUM

Science>Physics>Thermionic Emission and Radioactivity>Work Function

In the experimental set up to show thermionic electron emission, there are deflecting plates, fluorescent screen, variable resistance.

MEDIUM

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Explain the experimental set up to produce thermionic electron emission.

HARD

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Draw a cathode ray tube consisting of a heater, a cathode, a cylindrical anode and a deflecting system. Why are materials of low work function preferred as thermionic cathode materials?

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Name a substance that is a good thermionic emitter.

HARD

Science>Physics>Thermionic Emission and Radioactivity>Work Function

Explain cathode ray tube with its applications.

EASY

Science>Physics>Thermionic Emission and Radioactivity>Work Function

State the characteristics required of a good thermion emitter.

The phenomenon of electron emission is defined as the emission of electrons from the surface that is caused by a change in temperature, radiation, or a strong electric field.

Important Questions on Thermionic Emission and Radioactivity

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