Modern Physics - NEET Physics Questions
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Modern Physics

Question 11: moderate

If the energy released in the fission of one nucleus is 200 MeV. Then the number of nuclei required per second in a power plant of 16 kW will be :

1. \[0.5\times 10^{14}\]
2. \[0.5\times 10^{12}\]
3. \[5\times 10^{12}\]
4. \[5\times 10^{14}\]
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Question 12: moderate

The velocity of the most energetic electrons emitted from a metallic surface is doubled when the frequency v of the incident radiation is doubled. The work function of this metal is :

1. hv/4
2. hv/3
3. hv/2
4. 2hv/3
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Question 13: moderate

Monochromatic light of frequency f1 is incident on a photocell and the stopping potential is found to be V1. What is the new stopping potential of the cell if it is radiated by monochromatic light of frequency f2 ?

1. \[V_{1}-\frac{h}{e}\left( f_{2}-f_{1} \right)\]
2. \[V_{1}+\frac{h}{e}\left( f_{2}+f_{1} \right)\]
3. \[V_{1}-\frac{h}{e}\left( f_{2}+f_{1} \right)\]
4. \[V_{1}+\frac{h}{e}\left( f_{2}-f_{1} \right)\]
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Question 14: moderate

Consider the following nuclear reactions and select the correct statements from the options that
follow.

(A) Free neutron has higher mass than proton, therefore reaction I is possible
(B) Free proton has less mass than neutron, therefore reaction II is not possible for the free
proton
(C) Inside a nucleus, both decays (reaction I and II) are possible
(D) Inside a nucleus, reaction I is not possible but reaction II is possible.

1. A, B, C are correct
2. A, C, D are correct
3. A, B, D are correct
4. B, C, D are correct
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Question 15: moderate

Mark the incorrect statement :

1. Following alpha or beta decay a nucleus reaches its ground state after emitting nuclear gamma rays.
2. A proton can not decay to a neutron in a nuclei because such decay has negative Q value of reaction.
3. A positron can capture electron resulting in gamma rays photon only.
4. In positive beta decay the emitted positron shows continuous distribution of kinetic energy.
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Question 16: moderate

The correct graph between the maximum energy of a photoelectron and the inverse of wavelength of the incident radiation is given by the curve

1. A
2. B
3. C
4. None of the above
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Question 17: moderate

A photon of wavelength 6630 Å is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

1. \[6.63\times 10^{-27}kg-m/sec\]
2. \[2\times 10^{-27}kg-m/sec\]
3. \[10^{-27}kg-m/sec\]
4. \[3\times 10^{-27}kg-m/sec\]
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Question 18: moderate

The ratio of de-Broglie wavelengths of molecules of hydrogen and helium which are at temperature 27°C and 127° respectively is :

1. 1/2
2. \[\sqrt{\frac{3}{8}}\]
3. \[\sqrt{\frac{8}{3}}\]
4. 1
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Question 19: moderate

What is energy released in the β-decay of \[^{32}P\longrightarrow ^{32}S\] ?

\[\left( Given:atomic masses:-31.97391amu for ^{32}P and 31.97207amu for ^{32}S \right)\]

1. –1.2 Mev
2. +1.7 Mev
3. +2.1 Mev
4. –0.9 Mev
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Question 20: moderate

The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as given below :

1.
2.
3.
4.
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