In the context of quantum mechanics, how is the term 'photon' related to the term 'quantum'?

• A. A photon is a quantum of gravitational energy.
• B. A photon is the smallest possible unit of matter.
• C. A quantum is a particle of light called a photon.
• D. A photon is a quantum of electromagnetic energy.

Answer: (D)

Verified step by step guidance

1. Understand the term 'quantum' in quantum mechanics: it refers to the smallest discrete unit of any physical property, such as energy.
2. Recognize that electromagnetic energy, like light, is quantized, meaning it exists in discrete packets rather than a continuous flow.
3. Identify that a 'photon' is the name given to the quantum of electromagnetic energy, meaning it is the smallest unit or packet of light energy.
4. Clarify that a photon is not a unit of gravitational energy nor the smallest unit of matter; it specifically relates to electromagnetic radiation.
5. Summarize that the correct relationship is: a photon is a quantum of electromagnetic energy, linking the concept of 'quantum' to the particle nature of light.