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Calculate the number of photons, from green light of mercury (ʎ = 4961 Å), required to do one joule of work?

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Calculate the number of photons, from green light of mercury (ʎ = 4961 Å), required to do one joule of work? Answer: 2.4961×10^18/m^3

The correct answer is 2.4961×10¹⁸/m³, based on the numerical value derived from the calculation. Approximately \(2.496\times 10^{18}\) photons are required to produce one joule of work. The number of photons can be determined by first calculating the energy of a single photon and then dividing the total required energy (one joule) by the energy of that single photon

Question context

This question is part of ⚙️ Mechanical Eng within the broader 🛠️ Engineering Essentials subject and appears in the SPSC – Sindh Public Service Commission preparation collection. Reviewing the answer together with nearby questions helps reinforce the underlying concept and identify how it may appear in competitive exams.