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

2026 30 questions

1. Q472026 · 23 Jan 2026 · Shift 2· Numerical answer

   The average energy released per fission for the nucleus of ${}_{92}^{235}\text{U}$ is 190 MeV . When all the atoms of 47 g pure ${}_{92}^{235}\text{U}$ undergo fission process, the energy released is $\alpha \times 10^{23}\text{MeV}$. The value of $\alpha$ is _____. (Avogadro Number $=6\times 10^{23}$ per mole)

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   Answer: 228

2. Q412026 · 22 Jan 2026 · Shift 1

   The minimum frequency of photon required to break a particle of mass 15.348 amu into $4\alpha$ particles is ____ kHz . [mass of He nucleus = $4.002\mathrm{amu},1\mathrm{amu}=1.66\times 10^{-27}\mathrm{kg},\mathrm{h}=6.6\times 10^{-34}J.s$ and $\mathrm{c}=3\times 10^{8}m/s$ ]

   1. A.$14.94\times 10^{20}$
   2. B.$9\times 10^{19}$
   3. C.$9\times 10^{20}$
   4. D.$14.94\times 10^{19}$
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   Answer: D

3. Q432026 · 22 Jan 2026 · Shift 1

   $7.9\mathrm{MeV}\alpha$-particle scatters from a target material of atomic number 79 . From the given data the estimated diameter of nuclei of the target material is (approximately) ____ m. $\left[\frac{1}{4\pi {ϵ}_o}=9\times 10^9\mathrm{N}{\mathrm{m}}^2/{\mathrm{C}}^2\text{ and electron charge }=1.6\times 10^{-19}\mathrm{C}\right]$

   1. A.$2.88\times 10^{-14}$
   2. B.$5.76\times 10^{-14}$
   3. C.$1.44\times 10^{-13}$
   4. D.$1.69\times 10^{-12}$
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   Answer: B

4. Q402026 · 21 Jan 2026 · Shift 1

   If an alpha particle with energy 7.7 MeV is bombarded on a thin gold foil, the closest distance from nucleus it can reach is ____ m. (Atomic number of gold $=79$ and $\frac{1}{4\pi {ϵ}_o}=9\times 10^9$ in SI units)

   1. A.$2.95\times 10^{-16}$
   2. B.$3.85\times 10^{-14}$
   3. C.$2.95\times 10^{-14}$
   4. D.$3.85\times 10^{-16}$
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   Answer: C

5. Q372026 · 21 Jan 2026 · Shift 2

   The energy of an electron in an orbit of the Bohr's atom is $-0.04E_0$ eV where $E_0$ is the ground state energy. If $L$ is the angular momentum of the electron in this orbit and $h$ is the Planck's constant, then $\frac{2\pi L}{h}$ is ____ :

   1. A.6
   2. B.2
   3. C.5
   4. D.4
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   Answer: C