Dual Nature, Atoms & Nuclei · JEE Main previous year questions

295 questions asked across 20 exam years, newest first

Year-wise papers Topic-wise questions

Practise this topic

2023 55 questions

Q362023 · 13 Apr 2023 · Shift 1
The difference between threshold wavelengths for two metal surfaces A and B having work function $ϕ_{A} = 9 eV$ and $ϕ_{B} = 4.5 eV$ in nm is: { Given, $h c = 1242 eV nm$ }
1. A. $264$
2. B. $138$
3. C. $540$
4. D. $276$
Show answer
Answer: B
Q412023 · 13 Apr 2023 · Shift 1
$_{92}^{238} A \to_{90}^{234} B +_{2}^{4} D + Q$ In the given nuclear reaction, the approximate amount of energy released will be: [Given, mass of $_{92}^{238} A = 238.05079 \times 931.5 MeV / c^{2}$ , mass of $_{90}^{234} B = 234.04363 \times 931.5 MeV / c^{2}$ , mass of $_{2}^{4} D = 4.00260 \times 931.5 MeV / c^{2}$ ]
1. A. $2.12 MeV$
2. B. $4.25 MeV$
3. C. $3.82 MeV$
4. D. $5.9 MeV$
Show answer
Answer: B
Q532023 · 13 Apr 2023 · Shift 1· Numerical answer
The radius of $2^{nd}$ orbit of $He^{+}$ of Bohr's model is $r_{1}$ and that of fourth orbit of $Be^{3 +}$ is represented as $r_{2}$ . Now the ratio $\frac{r _{2}}{r _{1}}$ is $x : 1$ . The value of $x$ is ___________.
Show answer
Answer: 2
Q492023 · 13 Apr 2023 · Shift 2
Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$ Assertion A : The binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range 30 to 170 . Reason R : Nuclear force is short ranged. In the light of the above statements, choose the correct answer from the options given below
1. A.A is false but $R$ is true
2. B.A is true but $R$ is false
3. C.Both $A$ and $R$ are true and $R$ is the correct explanation of $A$
4. D.Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$
Show answer
Answer: C
Q522023 · 13 Apr 2023 · Shift 2· Numerical answer
An atom absorbs a photon of wavelength $500 nm$ and emits another photon of wavelength $600 nm$ . The net energy absorbed by the atom in this process is $n \times 1 0^{- 4} eV$ . The value of $n$ is ___________. [Assume the atom to be stationary during the absorption and emission process] (Take $h = 6.6 \times 1 0^{- 34} Js$ and $c = 3 \times 1 0^{8} m/s$ )
Show answer
Answer: 4125
Q392023 · 12 Apr 2023 · Shift 1
A proton and an $α$ -particle are accelerated from rest by $2 V$ and $4 V$ potentials, respectively. The ratio of their de-Broglie wavelength is :
1. A. $4 : 1$
2. B. $2 : 1$
3. C. $8 : 1$
4. D. $16 : 1$
Show answer
Answer: A
Q452023 · 12 Apr 2023 · Shift 1
A $12.5 eV$ electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be:
1. A. $2$
2. B. $4$
3. C. $3$
4. D. $1$
Show answer
Answer: C
Q582023 · 12 Apr 2023 · Shift 1· Numerical answer
A common example of alpha decay is $_{92}^{238} U ⟶_{90}^{234} Th +_{2}^{4} He + Q$ Given : $_{92}^{238} U = 238.05060 u$ , $_{90}^{234} Th = 234.04360 u$ , $_{2}^{4} He = 4.00260 u$ and $1 u = 931.5 \frac{MeV}{c ^{2}}$ The energy released ( $Q$ ) during the alpha decay of $_{92}^{238} U$ is _________ $MeV$
Show answer
Answer: 4
Q432023 · 11 Apr 2023 · Shift 1
A metallic surface is illuminated with radiation of wavelength $λ$ , the stopping potential is $V_{0}$ . If the same surface is illuminated with radiation of wavelength $2 λ$ . the stopping potential becomes $\frac{V _{0}}{4}$ . The threshold wavelength for this metallic surface will be
1. A. $3 λ$
2. B. $4 λ$
3. C. $\frac{3}{2} λ$
4. D. $\frac{λ}{4}$
Show answer
Answer: A
Q492023 · 11 Apr 2023 · Shift 1
Two radioactive elements A and B initially have same number of atoms. The half life of A is same as the average life of B. If $λ_{A}$ and $λ_{B}$ are decay constants of A and B respectively, then choose the correct relation from the given options.
1. A. $λ_{A} = λ_{B} ln 2$
2. B. $λ_{A} ln 2 = λ_{B}$
3. C. $λ_{A} = 2 λ_{B}$
4. D. $λ_{A} = λ_{B}$
Show answer
Answer: A
Q592023 · 11 Apr 2023 · Shift 1· Numerical answer
A monochromatic light is incident on a hydrogen sample in ground state. Hydrogen atoms absorb a fraction of light and subsequently emit radiation of six different wavelengths. The frequency of incident light is $x \times 1 0^{15} Hz$ . The value of $x$ is _________. (Given $h = 4.25 \times 1 0^{- 15} eV s$ )
Show answer
Answer: 3
Q362023 · 11 Apr 2023 · Shift 2
The energy of $He^{+}$ ion in its first excited state is, (The ground state energy for the Hydrogen atom is $- 13.6 eV$ ) :
1. A. $- 13.6 eV$
2. B. $- 27.2 eV$
3. C. $- 3.4 eV$
4. D. $- 54.4 eV$
Show answer
Answer: A
Q392023 · 11 Apr 2023 · Shift 2
The ratio of the de-Broglie wavelengths of proton and electron having same Kinetic energy : (Assume $m_{p} = m_{e} \times 1849$ )
1. A. $1 : 43$
2. B. $1 : 62$
3. C. $2 : 43$
4. D. $1 : 30$
Show answer
Answer: A
Q562023 · 11 Apr 2023 · Shift 2· Numerical answer
A nucleus disintegrates into two nuclear parts, in such a way that ratio of their nuclear sizes is $1 : 2^{1/3}$ . Their respective speeds have a ratio of $n : 1$ . The value of $n$ is _________.
Show answer
Answer: 2
Q392023 · 10 Apr 2023 · Shift 1
The de Broglie wavelength of a molecule in a gas at room temperature (300 K) is $λ_{1}$ . If the temperature of the gas is increased to 600 K, then the de Broglie wavelength of the same gas molecule becomes
1. A. $2 λ_{1}$
2. B. $\frac{1}{2} λ_{1}$
3. C. $\frac{1}{2} λ_{1}$
4. D. $2 λ_{1}$
Show answer
Answer: C
Q442023 · 10 Apr 2023 · Shift 1
The angular momentum for the electron in the first Bohr orbit is L. If the electron is assumed to revolve in second orbit of hydrogen atom, then the change in angular momentum will be
1. A.L
2. B. $\frac{L}{2}$
3. C.zero
4. D.2 L
Show answer
Answer: A
Q602023 · 10 Apr 2023 · Shift 1· Numerical answer
The decay constant for a radioactive nuclide is $1.5 \times 1 0^{- 5} s^{- 1}$ . Atomic weight of the substance is $60 g mole^{- 1}$ , ( $N_{A} = 6 \times 1 0^{23}$ ). The activity of $1.0 μ g$ of the substance is _________ $\times 1 0^{10} Bq$ .
Show answer
Answer: 15
Q452023 · 10 Apr 2023 · Shift 2
1. A.1.36 eV
2. B.18.6 eV
3. C.2.98 eV
4. D.2.07 eV
Show answer
Answer: D
Q492023 · 10 Apr 2023 · Shift 2
The half life of a radioactive substance is T. The time taken, for disintegrating $\frac{7}{8} th$ part of its original mass will be:
1. A.8T
2. B.3T
3. C.T
4. D.2T
Show answer
Answer: B
Q602023 · 10 Apr 2023 · Shift 2· Numerical answer
If $917 \overset{˚}{A}$ be the lowest wavelength of Lyman series then the lowest wavelength of Balmer series will be _________ $\overset{˚}{A}$ .
Show answer
Answer: 3668
Q432023 · 8 Apr 2023 · Shift 1
For a nucleus $_{Z}^{A} X$ having mass number $A$ and atomic number $Z$ A. The surface energy per nucleon $(b_{s}) = - a_{1} A^{2/3}$ . B. The Coulomb contribution to the binding energy $b_{c} = - a_{2} \frac{Z ( Z - 1 )}{A ^{4/3}}$ C. The volume energy $b_{v} = a_{3} A$ D. Decrease in the binding energy is proportional to surface area. E. While estimating the surface energy, it is assumed that each nucleon interacts with 12 nucleons. ( $a_{1}, a_{2}$ and $a_{3}$ are constants) Choose the most appropriate answer from the options given below:
1. A.C, D only
2. B.B, C, E only
3. C.B, C only
4. D.A, B, C, D only
Show answer
Answer: A
Q472023 · 8 Apr 2023 · Shift 1
Proton ( $P$ ) and electron ( $e$ ) will have same de-Broglie wavelength when the ratio of their momentum is (assume, $m_{p} = 1849 m_{e}$ ):
1. A. $1 : 1$
2. B. $1 : 43$
3. C. $1 : 1849$
4. D. $43 : 1$
Show answer
Answer: A
Q542023 · 8 Apr 2023 · Shift 1· Numerical answer
A nucleus with mass number $242$ and binding energy per nucleon as $7.6 MeV$ breaks into two fragment each with mass number $121$ . If each fragment nucleus has binding energy per nucleon as $8.1 MeV$ , the total gain in binding energy is ___________ $MeV$ .
Show answer
Answer: 121
Q552023 · 8 Apr 2023 · Shift 2· Numerical answer
The ratio of wavelength of spectral lines $H_{α}$ and $H_{β}$ in the Balmer series is $\frac{x}{20}$ . The value of $x$ is ____.
Show answer
Answer: 27
Q392023 · 6 Apr 2023 · Shift 1
The kinetic energy of an electron, $α$ -particle and a proton are given as $4 K, 2 K$ and K respectively. The de-Broglie wavelength associated with electron ( $λ e$ ), $α$ -particle ( $λ α$ ) and the proton ( $λ p$ ) are as follows:
1. A. $λ α < λ p < λ e$
2. B. $λ α > λ p > λ e$
3. C. $λ α = λ p < λ e$
4. D. $λ α = λ p > λ e$
Show answer
Answer: A