Reason (R): Rest mass of a photon is zero.
Solution:
Concept: Fundamental properties of photons.
Formula: Energy-momentum relation \(E^2 = p^2c^2 + m_0^2c^4\). For a photon, \(m_0 = 0\).
Solution: Photons are the quanta of electromagnetic radiation and do not carry any electric charge. So (A) is true. Photons are massless particles, meaning their rest mass is zero. So (R) is true. The zero rest mass of a photon is intrinsically linked to its inability to carry charge and its nature as a mediator of the electromagnetic force. A charged particle must possess non-zero invariant mass for a consistent description in physics. Therefore, (R) provides a fundamental explanation for (A).
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