The work function of calcium is 2.14 eV. Find the threshold frequency for calcium.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 5.16 \times 10^{14}\,\mathrm{Hz} \)
The threshold frequency is the lowest frequency of light that can just eject electrons from the metal. A photon of this frequency has energy equal to the work function.
\( \displaystyle h\nu_0 = \phi_0 \;\Rightarrow\; \nu_0 = \frac{\phi_0}{h} \)
\( \phi_0 = 2.14\,\mathrm{eV} = 2.14 \times 1.6\times10^{-19}\,\mathrm{J} = 3.424\times10^{-19}\,\mathrm{J} \)
\( h = 6.63\times10^{-34}\,\mathrm{J\,s} \)
\( \displaystyle \nu_0 = \frac{3.424\times10^{-19}}{6.63\times10^{-34}} \approx 5.16\times10^{14}\,\mathrm{Hz} \)
Note: This question is from NCERT (2026-27). NTA sets numerical questions from NCERT too, so do not ignore NCERT while practising numericals.
NCERT (2026-27):
Particle Nature of Light: The Photon – …
