Q. No.A laser with a power output of \(2~\text{mW}\) operates at a wavelength of \(500~\text{nm}.\) The number of photons emitted per second is:
(Planck's constant, \(h=6.6\times 10^{-34}~\text{J-s}\) & speed of light, \(c=3.0\times 10^8~\text{m/s}\) )
1. \( 5 \times 10^{15} \)
2. \(1.5 \times 10^{16} \)
3. \(1 \times 10^{16} \)
4. \(2 \times 10^{16}\)
Subtopic: Particle Nature of Light |
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Two light sources emit \(\mathrm{X}\)-rays with a wavelength of \(1~\text{nm}\) and visible light with a wavelength of \(500~\text{nm},\) respectively. Both sources emit light with the same power of \(200~\text W.\) What is the ratio of the number density of photons of \(\mathrm{X}\)-rays to the number density of photons of visible light for the given wavelengths?
| 1. | \( \dfrac{1}{500} \) | 2. | \( 500 \) |
| 3. | \( \dfrac{1}{250} \) | 4. | \( 250\) |
Subtopic: Particle Nature of Light |
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Given below are two statements :
| Assertion (A): | Two photons having equal linear momenta have equal wavelengths. |
| Reason (R): | If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease. |
| 1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 3. | (A) is true but (R) is false. |
| 4. | (A) is false but (R) is true. |
Subtopic: Particle Nature of Light |
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If a substance absorbs \(500~\text{nm}\) wavelength radiation and emits radiation of wavelength \(600~\text{nm},\) then the net change in energy is: (take \(hc=1240~\text{eV-nm}\))
1. \(1.2\times10^{-3}~\text{eV}\)
2. \(3.0\times10^{-4}~\text{eV}\)
3. \(4.1\times10^{-1}~\text{eV}\)
4. \(5.2\times10^{-4}~\text{eV}\)
1. \(1.2\times10^{-3}~\text{eV}\)
2. \(3.0\times10^{-4}~\text{eV}\)
3. \(4.1\times10^{-1}~\text{eV}\)
4. \(5.2\times10^{-4}~\text{eV}\)
Subtopic: Particle Nature of Light |
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Average force exerted on a non-reflecting surface at normal incidence is \(2.4 \times 10^{-4} \mathrm{~N}.\) If \(360 \mathrm{~W} / \mathrm{cm}^2\) is the light energy flux during span of \(1\) hour \(30\) minutes, Then the area of the surface is:
1. \(0.02 \mathrm{~m}^2\)
2. \(0.2 \mathrm{~m}^2\)
3. \(20 \mathrm{~m}^2\)
4. \(0.1 \mathrm{~m}^2\)
1. \(0.02 \mathrm{~m}^2\)
2. \(0.2 \mathrm{~m}^2\)
3. \(20 \mathrm{~m}^2\)
4. \(0.1 \mathrm{~m}^2\)
Subtopic: Particle Nature of Light |
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If \(2.5 \times 10^{-6} ~\text N\) average force is exerted by a light wave on a non-reflecting surface area of \(30 ~\text{cm}^2\) during \(40~\text{minutes}\) of time span, the energy flux of light just before it falls on the surface is:
(Round off to the nearest integer, assume complete absorption and normal incidence conditions are there)
(Round off to the nearest integer, assume complete absorption and normal incidence conditions are there)
| 1. | \(15~\text{W/cm}^2\) | 2. | \(20~\text{W/cm}^2\) |
| 3. | \(25~\text{W/cm}^2\) | 4. | \(30~\text{W/cm}^2\) |
Subtopic: Particle Nature of Light |
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\(6\times10^5~\text{J} \) of electromagnetic energy is incident on a surface in time \(t_0.\) Then the total momentum imparted if the surface is completely absorbing is:
1. \(2 \times 10^{-3}~\text{kg-m/s}\)
2. \(10^{-3} ~\text{kg-m/s}\)
3. \(10^{-2}~\text{kg-m/s}\)
4. \(2 \times 10^{-4}~\text{kg-m/s}\)
1. \(2 \times 10^{-3}~\text{kg-m/s}\)
2. \(10^{-3} ~\text{kg-m/s}\)
3. \(10^{-2}~\text{kg-m/s}\)
4. \(2 \times 10^{-4}~\text{kg-m/s}\)
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If a bulb of power \(40~\text {W}\) is producing a light of wavelength \(\lambda=4000~\mathring A,\) then the number of photons emitted by the bulb per second is:
1. \(16\times10^{16}\)
2. \(8\times10^{19}\)
3. \(8\times10^{16}\)
4. \(24\times10^{15}\)
1. \(16\times10^{16}\)
2. \(8\times10^{19}\)
3. \(8\times10^{16}\)
4. \(24\times10^{15}\)
Subtopic: Particle Nature of Light |
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In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at \(10.2~\text{V}.\) The wavelength of light emitted by hydrogen atom when excited to the first excitation level is: (given \(hc = 1234\text{ eV-nm, e} = 1.6\times10^{-19}~\text{C}\)
1. \(100\) nm
2. \(110\) nm
3. \(122\) nm
4. \(105\) nm
1. \(100\) nm
2. \(110\) nm
3. \(122\) nm
4. \(105\) nm
Subtopic: Particle Nature of Light |
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The ratio of the power of a light source \(S_1\) to that the light source \(S_2\) is \(2.\) \(S_1\) is emitting \(2 × 10^{15}\) photons per second at \(600~\text{nm.}\) If the wavelength of the source \(S_2\) is \(300~\text{nm},\) then the number of photons per second emitted by \(S_2\) is _____ \(× 10^{14}\).
1. \(2\)
2. \(3\)
3. \(4\)
4. \(5\)
1. \(2\)
2. \(3\)
3. \(4\)
4. \(5\)
Subtopic: Particle Nature of Light |
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