Establish Einstein's relation 1 2 mu 2 = hv - hv 0 with respect to photoelectric emission.

The phenomenon of emission of electrons from a metal surface, when electromagnetic radiations of sufficiently high frequency are incident on it, is called the photoelectric effect. Einstein explained the photoelectric effect based on Planck's quantum theory according to which light radiation travels in the form of discrete photons. The energy of each photon is hv , where h is Planck's constant and v is the frequency of light. The main points of Einstein’s theory of the photoelectric effect are: The interaction between two particles results in photoelectric emission– one a photon of incident radiation and the other an electron of photosensitive metal. The free electrons are bound within the metal due to restraining forces on the surface. The minimum energy required to liberate an electron from the metal surface is called the work function W 0 of the metal. Each photon interacts with one electron. The energy hv of the incident photon is used up in two parts: A part of the energy of the photon is used in liberating the electron from the metal surface, which is equal to the work function W 0 of the metal, and The remaining energy of the photon is used in impairing kinetic energy to the ejected electron. Very few < 1 0 0 photons, whose energies are greater than W 0 , capable of ejecting the photons. By law of the conservation of energy, Energy of the incident photon = Maximum K . E . of photon + Work function hv = 1 2 mv 2 max + W 0 ∴ K max = 1 2 mv 2 max = hv - W 0 . . . . . . . ( 1 ) If the incident photon is threshold frequency v 0 , then its energy hv 0 is just sufficient to free the electron from the metal surface and does not give it any kinetic energy. So hv 0 = W 0 . Hence K max = 1 2 mv 2 max = hv - hv 0 = h v - v 0 . . . . . . ( 2 ) Equations (1) and (2) are called Einstein’s photoelectric equations.A

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What is the $K . E$ of photo electrons

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

EASY

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

Charge on an electron is

- 1.6 \times 10^{z}

coulomb. The value of

z

is _____.

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

Why is wave theory of electromagnetic radiation is not able to explain photo electric effect? How does photon picture resolve this problem?

MEDIUM

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

Establish Einstein's relation

\frac{1}{2} {mu}^{2} = hv - {hv}_{0}

with respect to photoelectric emission.

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

The force carrier in the case of

EM

waves is

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

Define threshold frequency.

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

Which one of the following particle is a boson?

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

A laser produces monochromatic light of wavelength

530.4 nm

. The power emitted is

3.0 mW

. The number of photons emitted per second on an average is

(h = 6.63 \times 10^{- 34} Js, c = 3 \times 10^{8} {ms}^{- 1})

MEDIUM

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

Light of frequency

8.41 \times 10^{14} H z

is incident on a metal surface. Electrons with a maximum speed of

7.5 \times 10^{5} m s^{- 1}

are ejected from the surface. Calculate the threshold frequency for photo emission of electrons. Also find the work function of the metal in electron volt (eV). Given, Planck's constant

h = 6.625 \times 10^{- 34} J s^{- 1}

and mass of the electron

m = 9.1 \times 10^{- 31} K g .

EASY

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

In the line spectra of hydrogen atom, difference between the largest and the shortest wavelengths of the Lyman series is

305 \overset{\circ}{A}

. The corresponding difference for the Paschan series in

\overset{\circ}{A}

is:________. (nearest integer)

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

State Heisenberg's Uncertainty principle.

EASY

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

Find the energy

(in eV)

of an X-ray photon of wavelength

λ = 1 \overset{o}{A}

MEDIUM

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

If the photoelectric effect is not seen with the ultraviolet radiations in a given metal, photo electrons may be emitted with the _____.

MEDIUM

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

Photoelectric effect represents:

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

Write any two applications of photoelectric cell.

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

What is "Photoelectric effect"?

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

In a photoelectric effect experiment, a point source of light of power

3.2 mW

emits photons each of which has

5 eV

energy. The source is located at a distance of

0.8 m

from the centre of a stationary metal disk having a work function of

3 eV .

The metal disk has a radius of

8 \times 10^{- 3} m .

Assuming that one photoelectron is emitted for every

10^{6}

photons striking the surface of the disk, how many photoelectrons are emitted every second?

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

What is meant by the dual nature of light?

EASY

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

If the work function for the photoelectron emission of a metal is

3.75 eV

, then the threshold wave length of the radiation needed for the ejection of the electron is approximately

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

The typical electric field required for electrons to be emitted from surfaces of metals by the "field emission" process is about

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

When photon of energy

4.0 eV

strikes the surface of a metal

A

, the elected photoelectrons have maximum kinetic energy

T_{A} eV

and de-Broglie wavelength

λ_{A}

. The maximum kinetic energy of photoelectron liberated from another metal

B

by photon of energy

4.50 eV

T_{B} = (T_{A} - 1.50) eV

. If the de-Broglie wavelength of these photoelectrons

λ_{B} = 2 λ_{A}

, then choose the correct statement(s).

What is the K.E of photo electrons

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

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What is the $K . E$ of photo electrons