Practice portal › Dual Nature of Matter and Radiation › Photon Energy, Number of Photons and Intensity
Asked in GUJCET 2026 · Photon energy, momentum and mass
Idea: from E = h u, h = E/u, so the unit of h is J÷s⁻¹ = J s.
In base units that is kg m² s⁻²×s = kg m² s⁻¹.
All four options are kg m² times some power of the second, so only that power decides: torque s⁻², angular momentum s⁻¹, power s⁻³, moment of inertia s⁰.
Angular momentum L = Iω is kg m²×s⁻¹ = kg m² s⁻¹, matching h exactly. That is no accident: Bohr's condition L = (nh)/(2π) only makes sense because h carries the unit of angular momentum.
So angular momentum has the same unit as Planck's constant.
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