Name em radiations used for detecting fake currency notes.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the type of electromagnetic radiation used to detect fake currency notes. This involves identifying which specific EM wave is employed in the process of authentication of currency.

2. **Identifying the Relevant EM Radiation**: Among the various types of electromagnetic waves (such as radio waves, microwaves, infrared, visible light, ultraviolet (UV), X-rays, and gamma rays), we need to focus on those that interact with the materials used in currency notes.

3. **Explaining the Mechanism**: Currency notes, especially those issued by the Reserve Bank of India (RBI), have specific features that can be checked for authenticity. One such feature is the use of ultraviolet (UV) light. When UV rays are directed onto the currency note, certain parts of the note will fluoresce or glow, indicating that it is genuine.

...