Physics

Electrons and Photons

158 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 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 physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

When accelerating voltage is increased from $10\ kV$ to $20\ kV$ in an X-ray tube, the gap between the wavelengths of $K _{\alpha}$ line and lowest end of continuous spectrum increases three times. The atomic number of the target element is:-

  1. $29$
  2. $27$
  3. $25$
  4. $23$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The shortest wavelength of the continuous spectrum is lambda_min = hc / eV. The gap between K-alpha and lambda_min is related to the accelerating voltage. Using Moseley's law and the given conditions, the atomic number Z can be solved.

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

Consider the following processes
(i) Electrical oscillation
(ii) Rapid deceleration of fast electrons
(iii) Atomic transition
Which of these are likely to produce visible light?

  1. (iii) only

  2. (ii) and (iii)

  3. (i) and (iii)

  4. (i), (ii) and (iii)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Visible light means i.e visible to human eye.

It runs about $700-400㎚$
So Basically all of these options
  1. Electrical oscillation
  2. Rapid deceleration of fast electrons
  3. Atomic transition
This is basically theoretical question.

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

A beam of electrons accelerated by a large potential difference $V$ is made to strike a metal target to produce $X-$rays. For which of the following values of $V$, the resulting $X-$rays have the lowest minimum wave length:

  1. $10\ KV$
  2. $20\ KV$
  3. $30\ KV$
  4. $40\ KV$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As we know, $\boxed{E _{max}=\dfrac{hc}{\lambda _{min}}}$

$\boxed{\lambda _{min}=\dfrac{hc}{ev}}$
Here the value of $v$ is given as $10kv,20kv,30kv,40kv$
A, $\boxed{\lambda \propto \dfrac{1}{V}}$, large value of $V$
$\Rightarrow$ min. value of $\lambda$
Hence for $40kv$, $\lambda _{min}$ is minimum.
$\therefore$ option $D$ is correct.

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

The operation of photodiodes, which convert light into electrical signals, relies on the physical principle of:

  1. Photoelectric Effect

  2. Conduction

  3. Superconductivity

  4. Band Theory of Solids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Photoelectric Effect enables the conversion of light energy into electrical signals in photodiodes.

Multiple choice

What is the name of the process by which high-energy electrons lose energy through collisions with atoms and molecules?

  1. Coulomb Scattering

  2. Inverse Compton Scattering

  3. Bremsstrahlung

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

Bremsstrahlung is the process by which high-energy electrons lose energy through collisions with atoms and molecules, resulting in the emission of photons.

Multiple choice

The photoelectric effect is the emission of electrons from a metal when light shines on it. Which of the following metals has the lowest work function?

  1. Sodium

  2. Potassium

  3. Cesium

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

Cesium has the lowest work function among the given metals, which means that it requires the least amount of energy to emit electrons.

Multiple choice

What is the principle of operation of a Geiger-Mueller counter?

  1. It detects the ionization of a gas caused by radiation

  2. It measures the amount of energy deposited by radiation

  3. It detects the emission of light by a scintillator material

  4. It measures the change in electrical resistance of a semiconductor material
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A Geiger-Mueller counter operates by detecting the ionization of a gas caused by radiation. When radiation interacts with the gas, it ionizes the gas molecules, creating free electrons and positive ions. These charged particles are then collected by electrodes, generating an electrical signal.

Multiple choice

What is the principle behind the operation of a DC glow discharge plasma source?

  1. Collisional ionization

  2. Secondary electron emission

  3. Thermionic emission

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

In a DC glow discharge plasma source, plasma is generated by collisional ionization of gas atoms by energetic electrons.

Multiple choice

What is the primary mechanism for plasma generation in a radio frequency discharge plasma source?

  1. Collisional ionization

  2. Secondary electron emission

  3. Thermionic emission

  4. Resonant absorption of electromagnetic waves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a radio frequency discharge plasma source, plasma is generated by the resonant absorption of electromagnetic waves by the gas atoms.

Multiple choice

What is the primary mechanism for plasma generation in a DC glow discharge plasma source?

  1. Collisional ionization

  2. Secondary electron emission

  3. Thermionic emission

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

In a DC glow discharge plasma source, plasma is generated by collisional ionization of gas atoms by energetic 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 energy difference between the conduction band and the valence band in a Quantum Well?

  1. The bandgap.

  2. The Fermi energy.

  3. The work function.

  4. The ionization energy.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The energy difference between the conduction band and the valence band in a Quantum Well is the bandgap. This is the energy required to excite an electron from the valence band to the conduction band.