Atoms And Nuclei - Modern Physics - Physics Previous Year Questions

1

2016 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2016

The wavelength of second Balmer line in hydrogen spectrum is 600 nm. The wavelength for its third line in Lyman series is

A

120 nm

B

600 nm

C

400 nm

D

200 nm

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2

2017 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2017

Radon-222 has a half-life of 3.8 days. If one starts with 0.064 kg of radon-222 left after 19 days will be

A

0.002 kg

B

0.062 kg

C

0.032 kg

D

0.024 kg

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3

2017 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2017

The de-Broglie wavelength of an electron is \(0.4 \times {10^{ - 10}}\) m when its kinetic energy is 1.0 keV. Its wavelength will be \(1.0 \times {10^{ - 10}}\) m, when its kinetic energy is

A

0.2 keV

B

0.8 keV

C

0.63 keV

D

0.16 keV

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4

2017 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2017

Let v_n and E_n be the respective speed and energy of an electron in the nth orbit of radius r_n, in a hydrogen atom, as predicted by Bohr's model. Then

A

plot of \({{{E_n}{r_n}} \over {{E_1}{r_1}}}\) as a function of n is a straight line of slope 0

B

plot of \({{{r_n}{v_n}} \over {{r_1}{v_1}}}\) as a function of n is a straight line of slope 1

C

plot of ln\(\left( {{{{r_n}} \over {{r_1}}}} \right)\) as a function of ln (n) is a straight line of slope 2

D

plot of ln \(\left( {{{{r_n}{E_1}} \over {{E_n}{r_1}}}} \right)\) as a function of ln (n) is a straight line of slope 4

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5

2018 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2018

An electron accelerated through a potential of 10000 V from rest has a de-Broglie wave length \(\lambda\). What should be the accelerating potential, so that the wavelength is doubled?

A

20000 V

B

40000 V

C

5000 V

D

2500 V

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6

2018 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2018

How the linear velocity v of an electron in the Bohr orbit is related to its quantum number n?

A

\(v \propto {1 \over n}\)

B

\(v \propto {1 \over {{n^2}}}\)

C

\(v \propto {1 \over {\sqrt n }}\)

D

\(v \propto n\)

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7

2018 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2018

If the half-life of a radioactive nucleus is 3 days, nearly what fraction of the initial number of nuclei will decay on the third day? (Given, \(\root 3 \of {0.25} \approx 0.63\))

A

0.63

B

0.5

C

0.37

D

0.13

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8

2019 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2019

A parent nucleus X undergoes \(\alpha\)-decay with a half-life of 75000 yrs. The daughter nucleus Y undergoes \(\beta\)-decay with a half-life of 9 months. In a particular sample, it is found that the rate of emission of \(\beta\)-particles is nearly constant (over several months) at \({10^7}/h\). What will be the number of \(\alpha\)-particles emitted in an hour?

A

10²

B

10⁷

C

10¹²

D

10¹⁴

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9

2019 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2019

To which of the following the angular velocity of the electron in the n-th Bohr orbit is proportional?

A

\({n^2}\)

B

\({1 \over {{n^2}}}\)

C

\({1 \over {{n^{3/2}}}}\)

D

\({1 \over {{n^3}}}\)

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10

2019 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2019

A proton and an electron initially at rest are accelerated by the same potential difference. Assuming that a proton is 2000 times heavier than an electron, what will be the relation between the de Broglie wavelength of the proton (\(\lambda\)_p) and that of electron (\(\lambda\)_e)?

A

\(\lambda = 2000{\lambda _e}\)

B

\({\lambda _p} = {{{\lambda _e}} \over {2000}}\)

C

\({\lambda _p} = 20\sqrt 5 {\lambda _e}\)

D

\({\lambda _p} = {{{\lambda _e}} \over {20\sqrt 5 }}\)

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11

2020 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2020

For nuclei with mass number close to 119 and 238, the binding energies per nucleon are approximately 7.6 MeV and 8.6 MeV, respectively. If a nucleus of mass number 238 breaks into two nuclei of nearly equal masses, what will be the approximate amount of energy released in the process of fission?

A

214 MeV

B

119 MeV

C

2047 MeV

D

1142 MeV

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12

2020 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2020

If R is the Rydberg constant in cm^-1, then hydrogen atom does not emit any radiation of wavelength in the range of

A

\({1 \over R}\) to \({4 \over {3R}}\) cm

B

\({7 \over 5R}\) to \({19 \over {5R}}\) cm

C

\({4 \over R}\) to \({36 \over {5R}}\) cm

D

\({9 \over R}\) to \({144 \over {7R}}\) cm

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13

2020 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2020

A nucleus X emits a \(\beta\)-particle to produce a nucleus Y. If their atomic masses are M_x and M_y respectively, then the maximum energy of the \(\beta\)-particle emitted is (where, m_e is the mass of an electron and c is the velocity of light)

A

\(({M_x} - {M_y} - {m_e}){c^2}\)

B

\(({M_x} - {M_y} + {m_e}){c^2}\)

C

\(({M_x} - {M_y} ){c^2}\)

D

\(({M_x} - {M_y} - {2m_e}){c^2}\)

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14

2021 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2021

Let r, v, E be the radius of orbit, speed of electron and total energy of electron respectively in H-atom. Which of the following quantities according to Bohr theory, is proportional to the quantum number n ?

A

vr

B

rE

C

\({r \over E}\)

D

\({r \over v}\)

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15

2021 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2021

A 12.5 eV electron beam is used to bombard gaseous hydrogen at ground state. The energy level upto which the hydrogen atoms would be excited is

A

2

B

3

C

4

D

1

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16

2022 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2022

Suppose in a hypothetical world the angular momentum is quantized to be even integral multiples of \({h \over {2\pi }}\). The largest possible wavelength emitted by hydrogen atoms in visible range in a world according to Bohr's model will be,

(Consider hc = 1242 Mev-fm)

A

153 nm

B

409 nm

C

121 nm

D

487 nm

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17

2022 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2022

If the kinetic energies of an electron, an alpha particle and a proton having same de-Broglie wavelength are \({\varepsilon _1},{\varepsilon _2}\) and \({\varepsilon _3}\) respectively, then

A

\({\varepsilon _1} > {\varepsilon _3} > {\varepsilon _2}\)

B

\({\varepsilon _1} = {\varepsilon _3} = {\varepsilon _2}\)

C

\({\varepsilon _1} < {\varepsilon _3} < {\varepsilon _2}\)

D

\({\varepsilon _1} > {\varepsilon _2} > {\varepsilon _3}\)

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18

2022 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2022

A sample of hydrogen atom in its ground state is radiated with photons of 10.2 eV energies. The radiation from the sample is absorbed by excited ionized He⁺. Thenwhich of the following statement/s is/are true?

A

He⁺ electron moves from n = 2 to n = 4.

B

In the He⁺ emission spectra, there will be 6 lines.

C

Smallest wavelength of He⁺ spectrum is obtained when transition taken place from n = 4 to n = 3.

D

He⁺ electron moves from n = 2 to n = 3.

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19

2023 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2023

A uniform magnetic field B exists in a region. An electron of charge q and mass m moving with velocity v enters the region in a direction perpendicular to the magnetic field. Considering Bohr angular momentum quantization, which of the following statements is/are true?

A

The radius of n^th orbit \(\mathrm{r_n~\infty ~\sqrt n}\).

B

The minimum velocity of the electron is \(\frac{\sqrt{\mathrm{qB} \hbar}}{\mathrm{m}}\).

C

Energy of the \(\mathrm{n}^{\text {th }}\) level \(E_{n} ~\infty~n\).

D

Transition frequency \(\omega\) between two successive levels is independent of n.

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20

2023 · Physics · Modern Physics · Atoms And Nuclei

WB JEE 2023

If the potential energy of a hydrogen atom in the first excited state is assumed to be zero, then the total energy of n = \(\infty\) state is,

A

3.4 eV

B

6.8 eV

C

0

D

\(\infty\)

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