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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 \(\text{hc} = 1240~\text{eV-nm}\)):
1. \(10^{20}\)
2. \(10^{25}\)
3. \(10^{30}\)
4. \(10^{40}\)
Subtopic: Particle Nature of Light |
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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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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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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, \(\nu_o.\) 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, \(\nu_o.\) The maximum kinetic energy of the emitted photoelectrons will be: (\(h\) is Planck's constant)
| 1. | Either \(\frac{h \omega_{1}}{2 \pi}\) or \(\frac{h \omega_{2}}{2 \pi}\) |
| 2. | Either\(\left(\frac{h \omega_{1}}{2 \pi}-h \nu_{0}\right)\) or \(\left(\frac{h \omega}{2 \pi}-h \nu_{0}\right)\) |
| 3. | \(\frac{h\left(\omega_{1}+\omega_{2}\right)}{2 \pi}-h \nu_{0}\) |
| 4. | Both \(\frac{h\left(\omega_{1}+\omega_{2}\right)}{2 \pi}-h \nu_{0}\) and \(\frac{h\left |\omega_{1}-\omega_{2}\right|}{2 \pi}-h \nu_{0}\) |
Subtopic: Einstein's Photoelectric Equation |
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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 \(\frac{1}{\lambda} \text { vs } \frac{1}{\lambda_{d}}\) is:
| 1. | a straight line passing through the origin. |
| 2. | a circle. |
| 3. | an ellipse. |
| 4. | a parabola. |
Subtopic: De-broglie Wavelength |
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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 vaccum):
1. \(\frac{\lambda{P}}{h c} f\)
2. \(\frac{2\lambda{P}}{h c} f\)
3. \(\frac{\lambda{P}}{h c} f e\)
4. \(\frac{2\lambda{P}}{h c} f e\)
1. \(\frac{\lambda{P}}{h c} f\)
2. \(\frac{2\lambda{P}}{h c} f\)
3. \(\frac{\lambda{P}}{h c} f e\)
4. \(\frac{2\lambda{P}}{h c} f e\)
Subtopic: Photoelectric Effect: Experiment |
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The graph which shows the variation of 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 |
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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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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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