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NEET 2012
Exam
NEET
Year
2012
Subject
Physics
Chapter
Dual Nature of Matter

NEET 2012 · Physics · Dual Nature of Matter

Monochromatic radiation emitted when electron on hydrogen atom...

Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V3.57 \mathrm{~V}. The threshold frequency of the material is

Options

  1. A4×1015 Hz4 \times 10^{15} \mathrm{~Hz}
  2. B5×1015 Hz5 \times 10^{15} \mathrm{~Hz}
  3. C1.6×1015 Hz1.6 \times 10^{15} \mathrm{~Hz}
  4. D2.5×1015 Hz2.5 \times 10^{15} \mathrm{~Hz}

Correct answer

C. 1.6×1015 Hz1.6 \times 10^{15} \mathrm{~Hz}

Step-by-step solution

Energy released from emission of electron E=(−3.4)−(−13.6)=10.2eV\begin{aligned} E & =(-3.4)-(-13.6) \\ & =10.2 \mathrm{eV} \end{aligned} From photo electric equation. Work function ϕ=E−eV=hvv=E−eVh=(10.2−3.57)e6.67×10−34v=6.63×1.6×10−196.67×10−34=1.6×1015 Hz\begin{aligned} \phi & =E-e V=h v \\ v & =\frac{E-e V}{h} \\ & =\frac{(10.2-3.57) e}{6.67 \times 10^{-34}} \\ v & =\frac{6.63 \times 1.6 \times 10^{-19}}{6.67 \times 10^{-34}} \\ & =1.6 \times 10^{15} \mathrm{~Hz} \end{aligned}
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