Write any one use of (i) photodiode (ii) LED.

Explanation

**Step-by-Step Solution:**

1. **Understanding Photodiode:**
- A photodiode is a semiconductor device that converts light into an electrical current. It operates on the principle of the photoelectric effect, where light photons generate electron-hole pairs in the semiconductor material.

2. **Use of Photodiode:**
- One common use of a photodiode is in optical signal detection. Photodiodes are widely used in applications such as fiber optic communication systems, where they detect light signals transmitted through optical fibers. They can measure different frequencies of light and are essential in light-operated switches.

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