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 dual nature of matter and radiation davisson and germer experiment and its conclusion matter waves wave nature of matter

In experiment of Davisson-Germer, emitted electron from filament is accelerated throguh voltage $V$ then de-Broglie wavelength of that electron will be ________ m .

  1. $\cfrac { 2eVm }{ \sqrt { h } } $
  2. $\cfrac { \sqrt { h } }{ 2Vem } $
  3. $\cfrac { \sqrt { 2Vem } }{ h } $
  4. $\cfrac { h }{ \sqrt { 2Vem } } $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Kinetic energy of the electron will be due to the voltage supplied.

$\cfrac { 1 }{ 2 } m{ v }^{ 2 }=eV$
$v=\sqrt { \cfrac { 2eV }{ m }  } $
We know that the wavelength is obtained as:
$\lambda =\cfrac { h }{ mv } $
$\quad \lambda =\cfrac { h }{ m\sqrt { \cfrac { 2eV }{ m }  }  } =\cfrac { h }{ \sqrt { 2eVm }  } $

Multiple choice physics dual nature of matter and radiation davisson and germer experiment and its conclusion matter waves wave nature of matter

In davisson-Germer experiment an electron beam accelerated with $54$ volt is diffracted at an angle of $$ by a nickel crystal and produced first diffraction maxima. The interatomic distance in Nickel crystal is  

  1. $1\mathop A\limits^0 $
  2. $2\mathop A\limits^0 $
  3. $2.15\mathop A\limits^0 $
  4. $3.12\mathop A\limits^0 $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the Davisson-Germer formula with 54 eV electrons (λ ≈ 1.67 Å) and the standard diffraction condition for nickel crystals, the interatomic distance is calculated to be approximately 2.15 Å, which matches the known lattice spacing of nickel.

Multiple choice physics dual nature of matter and radiation davisson and germer experiment and its conclusion matter waves wave nature of matter

In Davisson-Germer experiment an electron bear of energy 75 eV falls normally on the surface via crystal If the maxima of order I. _obtained at an angIe $45^o$ to the direction incidentr then the interatomic distance in the lattice palne of the cystal will be-

  1. $1.0 \ AA$
  2. $1.56 \ AA$
  3. $1.20 \ AA$
  4. $0.83 \ AA$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} nb=2d\sin  \theta  \ \frac { { 12.27 } }{ { \sqrt { 75 }  } } =2d\sin  45 \ 1.41=2d\times \frac { 1 }{ { \sqrt { 2 }  } }  \ \therefore d=\frac { { 1.41 } }{ { 1.41 } } =1A^{ ^{ \circ  } } \end{array}$

Hence, the option $A$ is the correct answer.

Multiple choice physics dual nature of matter and radiation davisson and germer experiment and its conclusion matter waves wave nature of matter

In Davisson-Germer experiment, intensity was maximum for accelerating voltage equal to

  1. $44$
  2. $54$
  3. $64$
  4. $74$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In Davisson-Germer experiment, maximum intensity of diffracted electron beam was found at different angles by varying the applied voltage to the electron gun. The highest intensity was observed at an angle $\phi =50^o$ with a voltage of $54 V$, giving the electron a kinetic energy of $54eV$.

Multiple choice physics dual nature of matter and radiation davisson and germer experiment and its conclusion matter waves wave nature of matter

The Davisson-Germer experiment was performed by varying the accelarating voltage from __ V to __ V.

  1. $44, 68$
  2. $54, 78$
  3. $44, 58$
  4. $85, 100$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In Davisson-Germer experiment, maximum intensity of diffracted electron beam was found at different angles by varying the applied voltage to the electron gun from $44V$ to $68V$. The highest intensity was observed at an angle $\phi =50^o$ with a voltage of $54 V$, giving the electron a kinetic energy of $54eV$.

Multiple choice the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

The maximum kinetic energy of electron if wavelength of incident electromagnetic wave is $260 \,nm$ and cut-off wavelength is $380 \,nm$ given $hc = 1237 \,nm-eV$ is

  1. $1.5 \,eV$
  2. $6.4 \,eV$
  3. $10 \,eV$

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We know 
$KE _{max} = \dfrac{hc}{\lambda} - \dfrac{hc}{\lambda _0} $
$= \dfrac{1237 \, nm. eV}{260 \, nm} - \dfrac{1237 \, nm . eV}{380 \, nm}$
$= 1.5 eV$

Multiple choice detection and recording of x-ray images option c: imaging physics

Consider a metal used to produced some characteristic $X-$rays. Energy of $X-$ray are given by $E$ and wavelength as represented by $\lambda$. Then which of the following is true:

  1. $E(K _{\alpha}) > E({K} _{\beta}) > E(K _{\gamma})$
  2. $E(M _{\alpha}) > E(L _{\alpha}) > E(K _{\alpha})$
  3. $\lambda (K _{\alpha}) > \lambda (K _{\beta}) > \lambda (K _{\gamma})$
  4. $\lambda (M _{ \alpha })>\lambda (L _{ \alpha })>\lambda (K _{ \alpha })$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice detection and recording of x-ray images option c: imaging physics

The shortest wavelength of X-rays emitted from an X-ray tube depends on

  1. The current in tube

  2. The voltage applied to the tube

  3. The nature of the gas in tube

  4. The atomic number of the target material
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The shortest wavelength (lambda_min) of X-rays is determined by the Duane-Hunt law, which states that lambda_min = hc / eV. This shows that the minimum wavelength depends inversely on the accelerating voltage (V).

Multiple choice detection and recording of x-ray images option c: imaging physics

Consider the following statements A and B, identify the correct choice in the given answers. 

A) Tightly bound electrons of target material scatter X-ray photon,resulting in the Compton effect. 
B) Photoelectric effect takes place with free electrons.

  1. Both A and B are true

  2. A is true but B is false

  3. A is false but B is true

  4. Both A and B are false
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Compton effect happens with free electrons.
Photoelectric effect happens to bounded electrons.

Multiple choice detection and recording of x-ray images option c: imaging physics

For Compton effect with visible light the observed Compton shift is

  1. Very large because the electrons appear free

  2. Very small because the electrons appear free

  3. Is almost zero because the electrons appear bound

  4. Less than zero
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In compton scattering it is necessary that the energy of the photon should be very much greater than binding energy of electron. Binding energy is equal to work function of metal. In most of metals, the threshold frequency is equal to that of ultravoilet light that is why we do not observe comption effect with visible light.

Multiple choice detection and recording of x-ray images option c: imaging physics

A strong argument for the particle nature of cathode rays is that they

  1. travel through vacuum

  2. cast shadow

  3. get deflected by electric and magnetic field

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

The fact that cathode rays are deflected by electric and magnetic fields proves they consist of charged particles (electrons), as neutral waves would not be affected by these fields.

Multiple choice detection and recording of x-ray images option c: imaging physics

The particle nature of cathode rays is proved by

  1. Their deflection under magnetic/ electric field

  2. Colour of glow in gas discharge tube.

  3. Their propagation along a straight line.

  4. All of these.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is essentially the same question as 431450. Cathode rays (electrons) have charge and mass, which is proven by their deflection in electric and magnetic fields. Option A is correct. Colour of glow (B) depends on gas, not cathode rays. Straight-line propagation (C) and all options (D) don't specifically prove particle nature.

Multiple choice detection and recording of x-ray images option c: imaging physics

In Compton scattering
a) The modified line occurs because of scattering with a single electron
b) The unmodified line occurs because of scattering with the entire atom
c)The electron can recoil at an angle greater that $90^o$ .
d) The scattering photon and recoil electron can be projected on the same side of the incident direction

  1. a, b, c

  2. a, b, d

  3. b, c

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

The modified line occurs due to collision of photon with single electron.
Compton scattering usually refers to the interactive involving only the electrons of atoms,if  photon does not collide with any of electron of an atom, then it shows unmodified lines.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Particle nature and wave nature of electomagnetic waves can be shown by

  1. electron has small mass, deflected by the metal sheet

  2. X-ray is diffracted a, reflected by thick metal sheet

  3. light is refracted and diffracted

  4. light is polarised and shows photoelectric effect.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Polarization is a property unique to transverse waves (wave nature), while the photoelectric effect demonstrates the particle nature of light.