# 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.

Physics
Chemistry
Maths

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