JEE Main > Atoms and Nuclei

Explore popular questions from Atoms and Nuclei for JEE Main. This collection covers Atoms and Nuclei previous year JEE Main questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

If 13.6 eV energy is required to ionize the hydrogen atom, then the energy required to remove an electron from {tex} n = 2 {/tex} is

A

10.2{tex} \mathrm { eV } {/tex}

B

0{tex} e V {/tex}

3.4{tex} \mathrm { eV } {/tex}

D

6.8{tex} \mathrm { eV } {/tex}

Explanation







Q 2.    

Correct4

Incorrect-1

At absolute zero, Si acts as

A

non-metal

B

metal

insulator

D

none of these

Explanation

Q 3.    

Correct4

Incorrect-1

At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit
{tex} \begin{array} { l l } { \text { (i) electrons } } & { \text { (ii) protons } } \\ { \text { (iii) } \mathrm { He } ^ { 2 + } } & { \text { (iv) neutrons } } \end{array} {/tex}
The emission at instant can be

i, ii, iii

B

i, ii, iii, iv

C

iv

D

ii, iii

Explanation

Q 4.    

Correct4

Incorrect-1

Sodium and copper have work functions 2.3{tex} \mathrm { eV } {/tex} and 4.5{tex} \mathrm { eV } {/tex} respectively. Then the ratio of the wavelengths is nearest to

A

{tex} 1 : 2 {/tex}

B

{tex} 4 : 1 {/tex}

{tex} 2 : 1 {/tex}

D

{tex} 1 : 4 {/tex}

Explanation





Q 5.    

Correct4

Incorrect-1

Formation of covalent bonds in compounds exhibits

wave nature of electron

B

particle nature of electron

C

both wave and particle nature of electron

D

none of these

Explanation

Q 6.    

Correct4

Incorrect-1

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 substance left after 15 years is

{tex} N _ { 0 } / 8 {/tex}

B

{tex} N _ { 0 } / 16 {/tex}

C

{tex} N _ { 0 } / 2 {/tex}

D

{tex} N _ { 0 } / 4 {/tex}

Explanation



Q 7.    

Correct4

Incorrect-1

By increasing the temperature, the specific resistance of a conductor and a semiconductor

A

increases for both

B

decreases for both

increases, decreases

D

decreases, increases

Explanation









Q 8.    

Correct4

Incorrect-1

The energy band gap is maximum in

A

metals

B

superconductors

insulators

D

semiconductors.

Explanation

Q 9.    

Correct4

Incorrect-1

The part of a transistor which is most heavily doped to produce large number of majority carriers is

emmiter

B

base

C

collector

D

can be any of the above three.

Explanation

Q 10.    

Correct4

Incorrect-1

Which of the following are not electromagnetic waves?

A

cosmic rays

B

gamma rays

{tex} \beta {/tex} -rays

D

X-rays.

Explanation

Q 11.    

Correct4

Incorrect-1

A strip of copper and another of germanium are cooled from room temperature to 80{tex} \mathrm { K } {/tex} . The resistance of

A

each of these decreases

B

copper strip increases and that of germanium decreases

copper strip decreases and that of germanium increases

D

each of these increases

Explanation

Q 12.    

Correct4

Incorrect-1

Which of the following radiations has the least wavelength?

{tex} \gamma {/tex} -rays

B

{tex} \beta {/tex} -rays

C

{tex} \alpha {/tex} - rays

D

{tex} X {/tex} -rays

Explanation





Q 13.    

Correct4

Incorrect-1

When a {tex} {U} ^ {238} {/tex} nucleus originally at rest, decays by emitting an alpha particle having a speed '{tex} u {/tex} ', the recoil speed of the residual nucleus is

A

{tex} \frac { 4 u } { 238 } {/tex}

B

{tex} - \frac { 4 u } { 234 } {/tex}

{tex} \frac { 4 u } { 234 } {/tex}

D

{tex} - \frac { 4 u } { 238 } {/tex}

Explanation







Q 14.    

Correct4

Incorrect-1

The difference in the variation of resistance with temeperature in a metal and a semiconductor arises essentially due to the difference in the

A

crystal sturcture

variation of the number of charge carriers with temperature

C

type of bonding

D

variation of scattering mechanism with temperature

Explanation

Q 15.    

Correct4

Incorrect-1

A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is

0.4 {tex} \ln 2 {/tex}

B

0.2 {tex} \ln 2 {/tex}

C

0.1{tex} \ln 2 {/tex}

D

0.8 {tex} \ln 2 {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

A nucleus with {tex} Z = 92 {/tex} emits the following in a sequence: {tex} \alpha , \beta ^ { - } , \beta ^ { - } \alpha , \alpha , \alpha , \alpha , \alpha , \beta ^ { - } , \beta ^ { - } , \alpha , \beta ^ { + } , \beta ^ { + } , \alpha {/tex} Then {tex} Z {/tex} of the resulting nucleus is

A

76

78

C

82

D

74

Explanation







Q 17.    

Correct4

Incorrect-1

Two identical photocathodes receive light of frequencies {tex} f _ { 1 } {/tex} and {tex} { f _ { 2 }}{/tex} . If the velocites of the photo electrons (of mass m) coming out are respectively {tex} v _ { 1 } {/tex} and {tex} v _ { 2 } , {/tex} then

{tex} v _ { 1 } ^ { 2 } - v _ { 2 } ^ { 2 } = \frac { 2 h } { m } \left( f _ { 1 } - f _ { 2 } \right) {/tex}

B

{tex} v _ { 1 } + v _ { 2 } = \left[ \frac { 2 h } { m } \left( f _ { 1 } + f _ { 2 } \right) \right] ^ { 1 / 2 } {/tex}

C

{tex} v _ { 1 } ^ { 2 } + v _ { 2 } ^ { 2 } = \frac { 2 h } { m } \left( f _ { 1 } + f _ { 2 } \right) {/tex}

D

{tex} v _ { 1 } - v _ { 2 } = \left[ \frac { 2 h } { m } \left( f _ { 1 } - f _ { 2 } \right) \right] ^ { 1 / 2 } {/tex}

Explanation









Q 18.    

Correct4

Incorrect-1

Which of the following cannot be emitted by radioactive substances during their decay?

Protons

B

Neutrinoes

C

Helium nuclei

D

Electrons

Explanation

Q 19.    

Correct4

Incorrect-1

In the nuclear fusion reaction
{tex} ^ { 2 } \mathrm { H } + _ { 1 } ^ { 3 } \mathrm { H } \rightarrow _ { 2 } ^ { 4 } \mathrm { He } + n {/tex}
given that the repulsive potential energy between the two nuclei is {tex} \sim 7.7 \times 10 ^ { - 14 } \mathrm { J } {/tex} , the temperature at which the gases must be heated to initiate the reaction is nearly {tex} \left. \text { [Boltzmann's Constant } k = 1.38 \times 10 ^ { - 23 } \mathrm { J } / \mathrm { K } \right] {/tex}

A

{tex} 10 ^ { 7 } \mathrm { K } {/tex}

B

{tex} 10 ^ { 5 } \mathrm { K } {/tex}

C

{tex} 10 ^ { 3 } \mathrm { K } {/tex}

{tex} 10 ^ { 9 } \mathrm { K } {/tex}

Explanation







Q 20.    

Correct4

Incorrect-1

Which of the following atoms has the lowest ionization potential?

A

{tex} _ { 7 } ^ { 14 } \mathrm { N } {/tex}

{tex} _ { 55 } ^ { 133 } \mathrm { Cs } {/tex}

C

{tex} _ { 18 } ^ { 40 } \mathrm { Ar } {/tex}

D

{tex} _ { 8 } ^ { 16 } \mathrm { O } {/tex}

Explanation

Q 21.    

Correct4

Incorrect-1

The wavelengths involved in the spectrum of deuterium {tex} ({_l } {^ 2 } { D } ){/tex} are slightly different from that of hydrogen spectrum, because

A

the size of the two nuclei are different

B

the nuclear forces are different in the two cases

the masses of the two nuclei are different

D

the atraction between the electron and the nucleus is different in the two cases

Explanation





Q 22.    

Correct4

Incorrect-1

In the middle of the depletion layer of a reverse- biased {tex} p-n {/tex} junction, the

electric field is zero

B

potential is maximum

C

electric field is maximum

D

potential is zero

Explanation

Q 23.    

Correct4

Incorrect-1

If the binding energy of the electron in a hydrogen atom is 13.6{tex} \mathrm { eV } {/tex} , the energy required to remove the electron from the first excited state of {tex} \mathrm { Li } ^ { + + } {/tex} is

30.6{tex} \mathrm { eV } {/tex}

B

13.6{tex} \mathrm { eV } {/tex}

C

3.4{tex} \mathrm { eV } {/tex}

D

122.4{tex} \mathrm { eV } {/tex}

Explanation





Q 24.    

Correct4

Incorrect-1

A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is

A

{tex} E c {/tex}

{tex}2 E / c {/tex}

C

{tex} E / C {/tex}

D

{tex} E / c ^ { 2 } {/tex}

Explanation





Q 25.    

Correct4

Incorrect-1

According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency, of the incident radiation gives as straight the whose slope

A

depends both on the intensity of the radiation and the metal used

B

depends on the intensity of the radiation

C

depends on the nature of the metal used

is the same for the all metals and independent of the intensity of the radiation

Explanation