Physics

Electrons and Photons

127 Questions

Electrons and photons are fundamental concepts in modern physics, focusing on quantum interactions and the photoelectric effect. The topic involves calculating work functions, kinetic energy, and photon wavelengths. These physics questions are highly relevant for competitive test preparation.

Photoelectric effectWork function calculationsPhoton energy and wavelengthElectron emissionAtomic transitions

Electrons and Photons Questions

Multiple choice physics quantum physics photons concept of photon photons and photoelectric effect

The work function of a certain metal is $3.31 \, \times \,  10^{-19} J.$ Then, the maximum kinetic energy of photoelectrons emitted by incident radiation of wavelength 5000 A is
$(Given\, h  = 6.62\times10^{-34} J-s, \, c= 3\times10^{-8} \, ms^{-1},\, e=  1.6 \times10^{-19} \, C)$

  1. $248 eV$
  2. $0.41 eV$
  3. $2.07 eV$
  4. $0.82 eV$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Work function $W _0 \, = \, 3.31 \, \times \, 10^{-19} \, J$
Wavelength of incident radiation
 $\lambda \, = \, 5000 \, \times \, 10^{-10} \, m$
$E \, = \, W _0 \, + \, KE$
(According to Einstein equation)
$\displaystyle \frac{hc}{\lambda} \, 3.31 \, \times \, 10^{-19} \, + \, KE$
$KE \, = \, - \, 3.31 \, \times \, 10^{-19} + \, \displaystyle \frac{6.62 \, \times \, 10^{-34} \, \times \, 3 \, \times \, 10^8}{5000 \, \times \, 10^{10}}$
$= \, - \, 3.31 \, \times \, 10^{-19} \, + \, 10^{-19} \, + \, \displaystyle \frac{6.62 \, \times \, 3}{5} \, \times \, 10^{-19}$
$= \, (- \, 3.31 \, \times \, 1.324 \, \times \, 3) \, \times \, 10^{-19}$
$= \, (3.972 \, - \, 3.31) \, \times \, 10^{-19} \, = \, 0.662 \, \times \, 10^{-19} \, J$
$\Rightarrow \, E \, = \, \displaystyle \frac{0.662 \, \times \, 10^{19}}{1.6 \, \times \, 10^{-19}} \, = \, 0.41 eV$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The phenomenon of pair production is :

  1. The production of an electron and a positron from $\gamma$ radiation

  2. Ejection of an electron from a metal surface when exposed to ultraviolet light

  3. Ejection of an electron from a nucleus

  4. Ionization of a neutral atom
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pair production :
Gamma rays of sufficient energy when passing near a nucleus disappear and materialize into pair of an electron and a positron.
To have pair production, minimum energy of $\gamma$ - ray radiation is 1.02MeV.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

A photon of $1.7 \times 10 ^{-13}$ joule is absorbed by a material under special circumstances. The correct statement is :

  1. Electron of the atoms of absorbed material will go the higher energy states.

  2. Electron and positron pair will be created

  3. Only positron pair will be produced

  4. Photoelectric effect will occur and electron will be produced
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For electron and positron pair production, minimum energy is $1.02\ MeV$.
Energy of photon is given: $ 1.7 \times 10^{-3} J=\dfrac{1.7 \times 10^{-13}}{1.6 \times 10^{-19}}$$=1.06 \, MeV$.
Since energy of photon is greater than 1.02 MeV, electron positron pair will be created.

Multiple choice difference between interference and diffraction explaining wave phenomena diffraction

When a certain photosensistive surface is illuminated with monochromatic light of frequency v, the stopping potential for the photo current is-${ V } _{ 0 }/2.$ When the surface frequency v/2, the stopping potential is -${ V } _{ 0 }.$ The threshold frequency for photoelectric emission is

  1. $\dfrac { 5v }{ 3 } $
  2. $2v$
  3. $\dfrac { 4 }{ 3 } v$
  4. $\dfrac { 3v }{ 2 } $
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Minimum energy that a $\gamma-ray$ must have to give rise to an electron-position pair is

  1. $0.51\ MeV$
  2. $1.02\ MeV$
  3. $2.04\ MeV$
  4. $1.53\ MeV$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pair production requires a photon with energy at least equal to the total rest mass energy of an electron and a positron. Each has a rest mass energy of approximately 0.51 MeV, so the minimum total energy needed is 2 times 0.51 MeV, which equals 1.02 MeV.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

A beam of ultraviolet light of all wavelengths passes through hydrogen gas at room temperature, in the $x-$direction. Assume that all photons emitted due to electron transitions inside the gas emerge in the $y-$direction. Let $A$ and $B$ denote the lights emerging from the gas in the $x-$ and $y-$directions respectively. Then,

  1. some of the incident wavelengths will be absent in $A$
  2. only those wavelengths will be present in $B$ which are absent in $A$
  3. $B$ will contain some visible light
  4. $B$ will contain some infrared light
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

$A, C, D$

Multiple choice

How does a CCD sensor convert light into an electrical signal?

  1. By absorbing photons and generating electrons

  2. By reflecting photons and generating electrons

  3. By transmitting photons and generating electrons

  4. By scattering photons and generating electrons
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A CCD sensor converts light into an electrical signal by absorbing photons and generating electrons.

Multiple choice

What is the primary mechanism responsible for the generation of plasmons in solids?

  1. Electronic transitions

  2. Vibrational transitions

  3. Rotational transitions

  4. Collective oscillations of free electrons
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In solids, plasmons are generated by the collective oscillations of free electrons, which can be excited by light or other electromagnetic radiation.

Multiple choice

What is the phenomenon of photon-electron interaction called?

  1. Compton scattering

  2. Photoelectric effect

  3. Pair production

  4. Bremsstrahlung
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The photoelectric effect is the phenomenon where a photon interacts with an electron in a material, causing the electron to be ejected from the material.

Multiple choice

What is the name of the process where a photon interacts with an electron, resulting in the emission of a new photon?

  1. Compton scattering

  2. Photoelectric effect

  3. Pair production

  4. Bremsstrahlung
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Compton scattering is the process where a photon interacts with an electron, causing the electron to recoil and the photon to change its wavelength.

Multiple choice

What is the process called where two photons interact to produce an electron and a positron?

  1. Compton scattering

  2. Photoelectric effect

  3. Pair production

  4. Bremsstrahlung
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pair production is the process where two photons interact to produce an electron and a positron.

Multiple choice

What is the name of the process where a charged particle is accelerated, emitting photons?

  1. Compton scattering

  2. Photoelectric effect

  3. Pair production

  4. Bremsstrahlung
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bremsstrahlung is the process where a charged particle is accelerated, emitting photons.

Multiple choice

The minimum energy required to remove an electron from a solid is called the:

  1. Work function

  2. Fermi level

  3. Density of states

  4. Band gap
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The minimum energy required to remove an electron from a solid is called the work function.

Multiple choice

Which property of a surface is related to the minimum energy required for an electron to escape from the surface?

  1. Work function

  2. Surface energy

  3. Surface roughness

  4. Contact angle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The work function of a surface is the minimum energy required for an electron to escape from the surface and enter the vacuum.