Name the phenomenon which shows the quantum nature of electromagnetic radiation.

Explanation

**Step-by-Step Solution:**

1. **Identify the Phenomenon**: The question asks for a phenomenon that demonstrates the quantum nature of electromagnetic radiation.

2. **Recall Relevant Concepts**: The photoelectric effect is a well-known phenomenon in physics that illustrates the quantum nature of light. It involves the emission of electrons from a material (usually a metal) when it is exposed to light of a certain frequency.

3. **Explain the Photoelectric Effect**: When light of a frequency greater than a certain threshold frequency strikes the surface of a metal, it can cause the ejection of electrons from that metal. This threshold frequency is specific to each material and is known as the work function.

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