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

2017 4 questions

1. Q432017 · 9 Apr 2017 · Shift 1

   A Laser light of wavelength 660 nm is used to weld Retina detachment. If a Laser pulse of width 60 ms and power 0.5 kW is used the approximate number of photons in the pulse are : [Take Planck's constant $\mathrm{h}=6.62\times 10^{-34}\mathrm{Js}$]

   1. A.$10^{20}$
   2. B.$10^{18}$
   3. C.$10^{22}$
   4. D.$10^{19}$
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   Answer: A

2. Q442017 · 9 Apr 2017 · Shift 1

   The acceleration of an electron in the first orbit of the hydrogen atom (n = 1) is :

   1. A.$\frac{h^2}{{\pi }^2{m}^2{r}^3}$
   2. B.$\frac{h^2}{8{\pi }^2{m}^2{r}^3}$
   3. C.$\frac{h^2}{4{\pi }^2{m}^2{r}^3}$
   4. D.$\frac{h^2}{4\pi m^2{r}^3}$
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   Answer: C

3. Q532017 · 8 Apr 2017 · Shift 1

   According to Bohr's theory, the time averaged magnetic field at the centre (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the ${\mathrm{n}}^{\mathrm{th}}$ orbit is proportional to : (n = principal quantum number)

   1. A.$n^{-4}$
   2. B.$n^{-5}$
   3. C.$n^{-3}$
   4. D.$n^{-2}$
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   Answer: B

4. Q542017 · 8 Apr 2017 · Shift 1

   Two deuterons undergo nuclear fusion to form a Helium nucleus. Energy released in this process is : (given binding energy per nucleon for deuteron = 1.1 MeV and for helium = 7.0 MeV)

   1. A.30.2 MeV
   2. B.32.4 MeV
   3. C.23.6 MeV
   4. D.25.8 MeV
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   Answer: C