NEET Modern Physics MCQs & PYQs

Q: If $ M(A, Z) $, $ M_p $ and $ M_n $ denote the masses of the nucleus $ ^A_Z X $, proton and neutron respectively in units of u (1 u = 931.5 $ MeV/c^2 $) and BE represents its binding energy in MeV, then: (2008)

The binding energy is given by $ B.E. = \Delta m c^2 = [Z M_p + (A-Z) M_n - M(A, Z)] c^2 $. Rearranging this gives the nuclear mass $ M(A,Z) = Z M_p + (A-Z) M_n - B.E./c^2 $.

Q: A nucleus $ ^A_Z X $ has mass represented by $ M(A, Z) $. If $ M_p $ and $ M_n $ denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then: (2007)

Binding energy is the energy equivalent of the mass defect. The mass defect is $ \Delta m = [Z M_p + (A-Z) M_n - M(A, Z)] $. Thus, the binding energy is $ B.E. = \Delta m c^2 = [Z M_p + (A-Z) M_n - M(A, Z)]c^2 $.

Q: A mixture consists of two radioactive materials $A_1$ and $A_2$ with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of $A_1$ and 160 g of $A_2$. The amount of the two in the mixture will become equal after: (2012 Pre)

Amounts remaining are equal: $40(1/2)^{t/20} = 160(1/2)^{t/10}$. This gives $(1/2)^{t/20 - t/10} = 4$, which means $2^{t/20} = 4 = 2^2$. Thus, $t/20 = 2$, yielding $t = 40 s$.

Q: A radioactive nucleus of mass M emits a photon of frequency $\nu$ and the nucleus recoils. The recoil energy will be (2011 Pre)

The momentum of the emitted photon is $p = h\nu/c$. By conservation of momentum, the nucleus recoils with the same momentum. Recoil energy $E = \frac{p^2}{2M} = \frac{h^2\nu^2}{2Mc^2}$.

Practice NEET Modern Physics Questions

Question 161:

easy

The binding energy per nucleon is maximum in case of

(1993)

The binding energy per nucleon curve peaks around mass number A = 56. Thus, $ _{26}^{56}Fe $ has the maximum binding energy per nucleon, which is approximately 8.8 MeV.

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Question 162:

easy

The energy equivalent of one atomic mass unit is

(1992)

By Einstein's mass-energy equivalence $ E = mc^2 $, a mass of 1 atomic mass unit (1 u) is equivalent to approximately 931.5 MeV of energy.

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Question 163:

easy

The mass of $ \alpha $-particle is

(1992)

An alpha particle is a helium nucleus consisting of two protons and two neutrons. Due to the mass defect which provides its binding energy, its total mass is less than the sum of the masses of its constituent individual nucleons.

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Question 164:

easy

If the nuclear force between two protons, two neutrons and between proton and neutron is denoted by $ F_{pp} $, $ F_{nn} $ and $ F_{pn} $ respectively, then

(1990)

The strong nuclear force is charge-independent. Therefore, the strong interaction is identical for proton-proton, neutron-neutron, and proton-neutron pairs, rendering them approximately equal ($ F_{pp} \approx F_{nn} \approx F_{pn} $) when ignoring minor Coulombic repulsion.

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Question 165:

easy

Which of the following statements is true for nuclear forces?

(1990)

Nuclear forces are the strongest forces in nature but they are strictly short-range forces, operating effectively only over distances of about 2 to 3 femtometers (fm). They do not follow the inverse square law.

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Question 166:

easy

The average binding energy of a nucleon inside an atomic nucleus is about

(1989)

For most stable nuclei with intermediate mass numbers (30 < A < 170), the average binding energy per nucleon is approximately 8 MeV.

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Question 167:

easy

If $ M(A, Z) $, $ M_p $ and $ M_n $ denote the masses of the nucleus $ ^A_Z X $, proton and neutron respectively in units of u (1 u = 931.5 $ MeV/c^2 $) and BE represents its binding energy in MeV, then:

(2008)

The binding energy is given by $ B.E. = \Delta m c^2 = [Z M_p + (A-Z) M_n - M(A, Z)] c^2 $. Rearranging this gives the nuclear mass $ M(A,Z) = Z M_p + (A-Z) M_n - B.E./c^2 $.

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Question 168:

easy

A nucleus $ ^A_Z X $ has mass represented by $ M(A, Z) $. If $ M_p $ and $ M_n $ denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then:

(2007)

Binding energy is the energy equivalent of the mass defect. The mass defect is $ \Delta m = [Z M_p + (A-Z) M_n - M(A, Z)] $. Thus, the binding energy is $ B.E. = \Delta m c^2 = [Z M_p + (A-Z) M_n - M(A, Z)]c^2 $.

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Question 169:

easy

A mixture consists of two radioactive materials $A_1$ and $A_2$ with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of $A_1$ and 160 g of $A_2$. The amount of the two in the mixture will become equal after:

(2012 Pre)

Amounts remaining are equal: $40(1/2)^{t/20} = 160(1/2)^{t/10}$. This gives $(1/2)^{t/20 - t/10} = 4$, which means $2^{t/20} = 4 = 2^2$. Thus, $t/20 = 2$, yielding $t = 40 s$.

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Question 170:

easy

A radioactive nucleus of mass M emits a photon of frequency $\nu$ and the nucleus recoils. The recoil energy will be

(2011 Pre)

The momentum of the emitted photon is $p = h\nu/c$. By conservation of momentum, the nucleus recoils with the same momentum. Recoil energy $E = \frac{p^2}{2M} = \frac{h^2\nu^2}{2Mc^2}$.

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