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Q. No.A fraction \(f\) of the incident energy in a beam of light of wavelength \(\lambda\) is absorbed by a metallic surface and causes photoemission. If the power of the beam falling on the surface is \(P\), then the maximum photocurrent is:
(\(e\) is electronic charge, \(h\) is Planck's constant, \(c\) is the velocity of light in vacuum)
1.
\(\dfrac{\lambda{P}}{h c} f\)
2.
\(\dfrac{2\lambda{P}}{h c} f\)
3.
\(\dfrac{\lambda{P}}{h c} f e\)
4.
\(\dfrac{2\lambda{P}}{h c} f e\)
Subtopic: Photoelectric Effect: Experiment |
57%
Level 3: 35%-60%
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Photons of wavelength \(\lambda\) cause the emission of photoelectrons from a metallic surface, the de-Broglie wavelength of the fastest photoelectron being \(\lambda_d\). A graph of \(\dfrac{1}{\lambda} \text { vs } \dfrac{1}{\lambda_{d}}\) is:
| 1. | a straight line passing through the origin. |
| 2. | a circle. |
| 3. | an ellipse. |
| 4. | a parabola. |
Subtopic: De-broglie Wavelength |
Level 3: 35%-60%
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The electric field associated with a light wave is given by \(E = E_0~ (\sin \omega_1 t)~ (\sin \omega_2 t)\).
This light wave falls on a metal having a threshold frequency, \(\nu_0.\) The maximum kinetic energy of the emitted photoelectrons will be: (\(h\) is Planck's constant)
This light wave falls on a metal having a threshold frequency, \(\nu_0.\) The maximum kinetic energy of the emitted photoelectrons will be: (\(h\) is Planck's constant)
| 1. | Either \(\dfrac{h \omega_{1}}{2 \pi}\) or \(\dfrac{h \omega_{2}}{2 \pi}\) |
| 2. | Either \(\left(\dfrac{h \omega_{1}}{2 \pi}-h \nu_{0}\right)\) or \(\left(\dfrac{h \omega}{2 \pi}-h \nu_{0}\right)\) |
| 3. | \(\dfrac{h\left(\omega_{1}+\omega_{2}\right)}{2 \pi}-h \nu_{0}\) |
| 4. | Both \(\dfrac{h\left(\omega_{1}+\omega_{2}\right)}{2 \pi}-h \nu_{0}\) and \(\dfrac{h\left |\omega_{1}-\omega_{2}\right|}{2 \pi}-h \nu_{0}\) |
Subtopic: Einstein's Photoelectric Equation |
Level 3: 35%-60%
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Photons of frequency \(\nu\) fill a room. A metallic plate having a work function \(W\) \((<h\nu)\) is moved with a velocity \(v\), in this room. The maximum energy of the emitted photoelectrons: (in the plate's frame)
| 1. | does not depend on \(v\) |
| 2. | increases as \(v\) increases |
| 3. | decreases as \(v\) increases |
| 4. | first increases and then decreases as \(v\) is increased |
Subtopic: Einstein's Photoelectric Equation |
57%
Level 3: 35%-60%
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The frequency of light in a photoelectric experiment is tripled. The stopping potential will:
| 1. | be tripled | 2. | be more than tripled |
| 3. | be less than tripled | 4. | become one-third |
Subtopic: Photoelectric Effect: Experiment |
55%
Level 3: 35%-60%
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Photons of light of wavelength, \(\lambda=400\) nm are incident on a composite photocathode consisting of multiple regions with metals having work functions of \(2.1\) eV and \(1.1\) eV. The emitted photoelectrons are sent through a retarding potential difference, \(V_0\). What is the minimum value of \(V_0\) required to stop all electrons? (take: \(hc=1240\) eV-nm)
| 1. | \(1\) V | 2. | \(1.5\) V |
| 3. | \(2\) V | 4. | \(5.2\) V |
Subtopic: Einstein's Photoelectric Equation |
53%
Level 3: 35%-60%
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A metallic ball (work function: \(2\) eV) is irradiated with light consisting of photons of wavelength \(200\) nm. The ball has an initial charge, giving it a potential \(1\) V. Take the product of Planck's constant and velocity of light, hc as \(1240\) eV-nm. The final potential of the ball, when photoemission practically stops, is:
1. \(2\) V
2. \(3.2\) V
3. \(4.2\) V
4. \(5.2\) V
1. \(2\) V
2. \(3.2\) V
3. \(4.2\) V
4. \(5.2\) V
Subtopic: Photoelectric Effect: Experiment |
53%
Level 3: 35%-60%
Hints
Photoelectrons emerging from a photocathode (work function: \(2.2~\text{eV}\)) are allowed to fall onto a gas containing hydrogen atoms in the ground state and the first excited state. What is the minimum energy of the photons incident on the photo-cathode that will cause the photoelectrons to transfer energy to the \(\mathrm{H\text-}\)atoms?
| 1. | \(13.6~\text{eV}+2.2~\text{eV}\) |
| 2. | \((10.2+2.2)~\text{eV}\) |
| 3. | \((3.4+2.2)~\text{eV}\) |
| 4. | \((1.89+2.2)~\text{eV}\) |
Subtopic: Photoelectric Effect: Experiment |
Level 4: Below 35%
Hints
\(A\) and \(B\) are two metals with threshold frequencies \(1.8\times 10^{14}\ \) Hz and \(2.2\times 10^{14}\ \) Hz. Two identical photons of energy \(0.825\) eV each are incident on them. Then, photoelectrons are emitted in:
(Take \(h=6.6\times 10^{-34}\ \) J-s)
1. \(B\) only
2. \(A\) only
3. neither \(A\) nor \(B\)
4. both \(A\) and \(B\)
(Take \(h=6.6\times 10^{-34}\ \) J-s)
1. \(B\) only
2. \(A\) only
3. neither \(A\) nor \(B\)
4. both \(A\) and \(B\)
Subtopic: Photoelectric Effect: Experiment |
Level 3: 35%-60%
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A photon of energy \(10.2\) eV corresponds to light of wavelength \(\lambda_0\). Due to electron transition from \(n = 2 \) to \(n = 1\) in a hydrogen atom, light of wavelength \(\lambda\) is emitted. If we take into account the recoil of atom when photon is emitted then:
| 1. | \(\lambda = \lambda_0\) |
| 2. | \(\lambda < \lambda_0\) |
| 3. | \(\lambda > \lambda_0\) |
| 4. | data is not sufficient to reach a conclusion |
Subtopic: Photoelectric Effect: Experiment |
Level 3: 35%-60%
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