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Q 1. The energy that should be added to an electron, to reduce its de-Broglie wavelengths from {tex} 10 ^ { - 10 } \mathrm { m } {/tex} to {tex} 0.5 \times 10 ^ { - 10 } \mathrm { m } , {/tex} will be
four times the initial energy.
thrice the initial energy.
equal to the initial energy.
twice the initial energy.
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Q 2. The probability of a radioactive atom for not disintegrating till 3 times of its half-life is
{tex} \frac { 1 } { 3 } {/tex}
{tex} \frac { 1 } { 4 } {/tex}
{tex} \frac { 1 } { 8 } {/tex}
{tex} \frac { 7 } { 8 } {/tex}
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Q 3. The wavelength of a certain line in the ray spectrum for tungsten {tex} ( Z = 74 ) {/tex} is 200 A. What would be the wavelength of the same line for platinum {tex} ( Z = 78 ) ? {/tex} The screening constant {tex} a {/tex} is unity.
179.76{tex} {\text{Å}} {/tex}
189.76{tex} {\text{Å}} {/tex}
289.76{tex} {\text{Å}} {/tex}
379.76{tex} {\text{Å}} {/tex}
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Q 4. Two electrons of kinetic energy 2.5 eV fall on a metal plate, which has work function of 4.0 eV. Number of electrons ejected from the metal surface is
One
Two
Zero
More than two
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Q 5. A proton with kinetic energy {tex} K {/tex} describes a circle of radius {tex} r {/tex} in a uniform magnetic field. An {tex} \alpha {/tex} -particle with kinetic energy {tex} K {/tex} moving in the same magnetic field will describe a circle of radius
{tex} \frac { r } { 2 } {/tex}
r
2{tex} r {/tex}
4{tex} r {/tex}
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Q 6. If the binding energy per nucleon is {tex}^{7}_{3}Li{/tex} and {tex}^{4}_{2}He{/tex} nuclei are 5.60 MeV and 7.06 MeV respectively, then in the reaction {tex}^{1}_{1}H + ^{7}_{3} Li \rightarrow 2 ^{4}_{2}He{/tex} energy of proton must be
39.2{tex} \mathrm { MeV } {/tex}
28.24{tex} \mathrm { MeV } {/tex}
17.28{tex} \mathrm { MeV } {/tex}
1.46{tex} \mathrm { MeV } {/tex}
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Q 7. In hydrogen like atoms the ratio of difference of energies {tex} E _ { 4 n } - E _ { 2 n } {/tex} and {tex} E _ { 2 n } - E _ { n } {/tex} varies with atomic number {tex} z {/tex} and principle quantum number {tex} n {/tex} as
{tex} \frac { z ^ { 2 } } { n ^ { 2 } } {/tex}
{tex} \frac { z ^ { 4 } } { n ^ { 4 } } {/tex}
{tex} \frac { z } { n } {/tex}
None of these
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Q 8. The ratio of de Broglie wavelength of {tex} \alpha {/tex} -particle to that of a proton being subjected to the same magnetic field so that the radii of their paths are equal to each other assuming the field induction vector {tex} \vec { B } {/tex} is perpendicular to the velocity vectors of the {tex} \alpha {/tex} -particle and the proton is
1
{tex} \frac { 1 } { 4 } {/tex}
{tex} \frac { 1 } { 2 } {/tex}
2
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Q 9. The speed of an electron having a wavelength of the order of 1{tex} {\text{Å}} {/tex} will be
{tex} 7.25 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}
{tex} 6.26 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}
{tex} 5.25 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}
{tex} 4.24 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } {/tex}
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Q 10. In certain element the {tex} K {/tex} -shell electron energy is {tex} - 18.525 \mathrm { keV } {/tex} and the {tex} L {/tex} -shell electron energy is {tex} - 3 \mathrm { keV } {/tex} . When an electron jumps from the {tex} L {/tex} -shell to {tex} K {/tex} shell, an {tex} x {/tex} -ray photon is emitted. The wavelength of the emitted {tex} x {/tex} -rays is
0.8{tex} {\text{Å}}{/tex}
1{tex} {\text{Å}}{/tex}
0.6{tex}{\text{Å}} {/tex}
1.2{tex} {\text{Å}} {/tex}
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Q 11. An electron moves along a metal tube with variable section. The velocity of the electron when it approaches the neck of tube, is
greater than {tex} v _ { 0 } {/tex}
equal to {tex} v _ { 0 } {/tex}
less than {tex} v _ { 0 } {/tex}
not defined
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Q 12. The probability of nucleus to decay in two mean lives is
{tex} \frac { 1 } { 4 } {/tex}
{tex} \frac { \mathrm { e } ^ { 2 } - 1 } { \mathrm { e } ^ { 2 } } {/tex}
{tex} \frac { 3 } { 4 } {/tex}
{tex} \frac { 1 } { e ^ { 2 } } {/tex}
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Q 13. A sample of radioactive material decays simultaneously by two processes {tex}\mathrm A {/tex} and {tex}\mathrm B {/tex} with half lives {tex} \frac { 1 } { 2 } {/tex} and {tex} \frac { 1 } { 4 } {/tex} hr respectively. For first half hr it decays with the process {tex} \mathrm A {/tex}, next one hr with the process {tex}\mathrm B {/tex} and for further half an hour with both {tex}\mathrm A {/tex} and {tex}\mathrm B {/tex}. If originally there were {tex}\mathrm N _ { 0 } {/tex} nuclei, find the number of nuclei after {tex} 2\ h r {/tex}, of such decay.
{tex} \frac { \mathrm { N } _ { 0 } } { ( 2 ) ^ { 8 } } {/tex}
{tex} \frac { \mathrm { N } _ { 0 } } { ( 2 ) ^ { 4 } } {/tex}
{tex} \frac { \mathrm { N } _ { 0 } } { ( 2 ) ^ { 6 } } {/tex}
{tex} \frac { \mathrm { N } _ { 0 } } { ( 2 ) ^ { 5 } } {/tex}
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Q 14. If {tex} N _ { 0 } {/tex} is the original mass of the substance of half-life period {tex} t _ { 1 / 2 } = 5 {/tex} years, then the amount of {tex} f {/tex} substance left after {tex}15{/tex} years is
{tex} N _ { 0 } / 8 {/tex}
{tex} N _ { 0 } / 16 {/tex}
{tex} N _ { 0 } / 2 {/tex}
{tex} N _ { 0 } / 4 {/tex}
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Q 15. Which of the following cannot be emitted by radioactive substances during their decay?
Protons
Neutrinoes
Helium nuclei
Electrons
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Q 16. Starting with a sample of pure {tex} ^{66} \mathrm { Cu } , \frac { 7 } { 8 } {/tex} of it decays into {tex} \mathrm { Zn } {/tex} in {tex}15{/tex} minutes. The corresponding half life is
{tex}15{/tex} minutes
{tex}10{/tex} minutes
{tex} 7 \frac { 1 } { 2 } {/tex} minutes
{tex}5{/tex} minutes
{tex}[\mathrm {OR}]{/tex}
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Q 17. In gamma ray emission from a nucleus
Only the proton number changes
Both the neutron number and the proton number change
There is no change in the proton number and the neutron number
Only the neutron number changes
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Q 18. This question contains {tex}\mathrm {Statement-1}{/tex} and {tex}\mathrm {Statement-2}{/tex}. Of the four choices given after the statements, choose the one that best describes the two statements.
{tex}\mathrm {Statement-1}{/tex}: Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion.
{tex}\mathrm {Statement-2}{/tex}:For heavy nuclei, binding energy per nucleon increases with increasing {tex} Z {/tex} while for light nuclei it decreases with increasing {tex} Z {/tex}
Statement-1 is false, Statement- 2 is true
Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement- - 1
Statement- 1 is true, Statement- 2 is true; Statement-2 is not a correct explanation for Statement- 1
Statement-l is true, Statement- 2 is false
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Q 19. The half life of a radioactive substance is {tex}20{/tex} minutes. The approximate time interval {tex} \left( t _ { 2 } - t _ { 1 } \right) {/tex} between the time {tex} t _ { 2 } {/tex} when {tex} \frac { 2 } { 3 } {/tex} of it had decayed and time {tex} t _ { 1 } {/tex} when {tex} \frac { 1 } { 3 } {/tex} of it had decayed is:
{tex} 14{/tex} {tex}\mathrm{ min } {/tex}
{tex} 20{/tex} {tex}\mathrm{ min } {/tex}
{tex} 28{/tex} {tex}\mathrm{ min } {/tex}
{tex} 7{/tex} {tex}\mathrm{ min } {/tex}
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Q 20. Assume that a neutron breaks into a proton and an electron. The energy released during this process is : (mass of neutron {tex} = 1.6725 \times 10 ^ { - 27 } \mathrm { kg }{/tex}, mass of proton {tex} = 1.6725 \times 10 ^ { - 27 } \mathrm { kg } , {/tex} mass electron {tex} \left. = 9 \times 10 ^ { - 31 } \mathrm { kg } \right) {/tex}
{tex} 0.51 {/tex} {tex}\mathrm { MeV } {/tex}
{tex} 7.10 {/tex} {tex}\mathrm { MeV } {/tex}
{tex}6.30 {/tex} {tex}\mathrm { MeV } {/tex}
{tex} 5.4 {/tex} {tex}\mathrm { MeV } {/tex}
