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QJEEM24Ph46bc: JEE Main 2024 Physics - Class 12 JEEM24Ph46bc Solution: The threshold frequency of a metal with work function is :

The threshold frequency of a metal with work function 6.63 eV6.63 \mathrm{~eV} is :

Multiple Choice Options

  • A 16×1015 Hz16 \times 10^{15} \mathrm{~Hz}
  • B 16×1012 Hz16 \times 10^{12} \mathrm{~Hz}
  • C 1.6×1015 Hz1.6 \times 10^{15} \mathrm{~Hz}
  • D 1.6×1012 Hz1.6 \times 10^{12} \mathrm{~Hz}

Step-by-Step Verified Solution

The threshold frequency, ν0\nu_0 , corresponds to the minimum frequency of light required to eject electrons from the surface of a metal, a phenomenon known as the photoelectric effect. The work function, represented by ϕ\phi , is the minimum energy needed to remove an electron from the surface of the metal.

The energy of a photon is given by the equation E=hνE = h\nu , where:

  • EE is the energy of the photon,
  • hh is Planck's constant ( h=6.626×10−34 J⋅sh = 6.626 \times 10^{-34} \, \text{J} \cdot \text{s} ), and
  • ν\nu is the frequency of the photon.

To find the threshold frequency for a metal with a work function of 6.63 eV6.63 \, \text{eV} , we must first express the work function in joules (since Planck's constant is in joules per second). To convert electron volts to joules, use the conversion factor 1 eV=1.602×10−19 J1 \, \text{eV} = 1.602 \times 10^{-19} \, \text{J} :

ϕ=6.63 eV×1.602×10−19 JeV=1.061×10−18 J\phi = 6.63 \, \text{eV} \times 1.602 \times 10^{-19} \, \frac{\text{J}}{\text{eV}} = 1.061 \times 10^{-18} \, \text{J}

The energy of the photon at the threshold frequency is equal to the work function:

hν0=ϕh\nu_0 = \phi

Solve for ν0\nu_0 :

ν0=ϕh=1.061×10−18 J6.626×10−34 J⋅s=1.6×1015 Hz\nu_0 = \frac{\phi}{h} = \frac{1.061 \times 10^{-18} \, \text{J}}{6.626 \times 10^{-34} \, \text{J} \cdot \text{s}} = 1.6 \times 10^{15} \, \text{Hz}

Thus, the correct answer is:

Option C 1.6×1015 Hz1.6 \times 10^{15} \, \text{Hz}

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