Q23 / 99 · NTA Abhyas (JEE Main) 2020 · Chemistry · Structure of Atom

A metal surface is illuminated by light of two different wavelengths  248 nm and 310 nm . The maximum speeds of the photoelectrons corresponding to these wavelengths are u1 and u2 respectively. If the ratio u1u2=21 and hc = 1240 eVnm , the work function of the metal is nearly

  • Correct answer
    A
    3.7 eV
  • B
    3.2 eV
  • C
    2.8 eV
  • D
    2.5 eV

Solution

As K.E∝v2
ratio of kinetic energy =41, as speed are in the ratio =21
K.E = Energy of incident photon – Work function (W)
4 KE=1240248-W   .....(i)
and  KE=1240310-W    .....(ii)
By solving (i) and (ii)
W=3.7 eV

Hence, the correct answer is option: 'A'.

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