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Q. No.A monochromatic source of light emits \(50~\text{W}\) at a wavelength of \(400~\text{nm}.\) The number of photons emitted per second is approximately (take \({hc} = 1240~\text{eV-nm}\)):
1. \(10^{20}\)
2. \(10^{25}\)
3. \(10^{30}\)
4. \(10^{40}\)
Subtopic: Particle Nature of Light |
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Level 1: 80%+
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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 |
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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 |
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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 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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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)
(\(e\) 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 |
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Level 3: 35%-60%
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The graph that shows the variation of the de-Broglie wavelength \((\lambda)\) of a particle and its associated momentum \((p)\) is:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
Subtopic: De-broglie Wavelength |
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In a photoelectric experiment, blue light is capable of ejecting a photoelectron from a specific metal while green light is not able to eject a photoelectron. Ejection of photoelectrons is also possible using light of the colour:
| 1. | yellow | 2. | red |
| 3. | violet | 4. | orange |
Subtopic: Photoelectric Effect: Experiment |
84%
Level 1: 80%+
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In an experiment on the photoelectric effect, the maximum kinetic energy of the emitted electrons is plotted as a function of the frequency of incident radiation. The graph is:
| 1. | a straight line with a positive intercept on the \(x\)-axis (frequency) |
| 2. | a straight line with a positive intercept on the \(y\)-axis (kinetic energy) |
| 3. | a parabola |
| 4. | a hyperbola |
Subtopic: Photoelectric Effect: Experiment |
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Level 2: 60%+
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Photons and electrons of the same wavelength are compared. Which one carries larger momentum?
| 1. | photon |
| 2. | electron |
| 3. | neither, since both have equal momenta |
| 4. | it could be either, depending on the energy |
Subtopic: De-broglie Wavelength |
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