Name the series of hydrogen spectrum lying in the infrared region.

The series of hydrogen spectrum lying in the infra-red region are Paschen series, Brackett series and Pfund series.
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Can a hydrogen atom absorb a photon having energy more than 13.6 eV?

Yes, a hydrogen atom can absorb a photon having energy more than 13.6 eV. But the atom should be ionised for this to happen.
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In a Rutherford's α-scattering experiment with thin gold foil, 8100 scintillations per minute are observed at an angle of 60°. What will be the number of scintillations per minute at an angle of 120°?


Given,
Number of scintillations per minute at an angle 60°, n1 = 8100 m
Number of scintillations per minute at an angle 120° , n2 =? 

The scattering in the Rutherford's experiment is proportional to cot4ϕ2. 

         n2n1 = cot4ϕ2/2cot4ϕ1/2  

Therefore,
 
          n2n1 = cot4120°2cot460°2         = cot 4 60°cot4 30°        = 1334         = 181 
This implies, 

       n2 = 181× n1     = 181×8100     =100.



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An element with atomic number Z = 11 emits K-X-ray of wavelength X. The atomic number of element which emits Ka-X-ray of wavelength 4λ is
  • 6

  • 4

  • 11

  • 44


A.

6

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A nucleus represented by the symbol ZXA has
  • Z protons and A neutrons
  • A protons and (Z – A) neutrons
  • Z neutrons and (A – Z) protons
  • Z protons and (A – Z) neutrons

D.

Z protons and (A – Z) neutrons
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