The electromagnetic waves detected using a thermopile and used in physical therapy are

Options

A. gamma radiations
B. X-rays
C. ultraviolet radiations
D. infrared radiations

Explanation

To solve the question regarding the electromagnetic waves detected using a thermopile and used in physical therapy, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Thermopile**:
- A thermopile is an electronic device that converts thermal energy into electrical energy. It is sensitive to infrared radiation, which is a type of electromagnetic wave.

2. **Identify the Options**:
- The options given are:
A. Gamma radiation
B. X-rays
C. Ultraviolet rays
D. Infrared radiation

3. **Analyze Each Option**:
- **Gamma Radiation**: Used primarily for sterilizing medical equipment. Not typically used in physical therapy.
- **X-rays**: Commonly used for imaging bones and detecting fractures. Not used in physical therapy.
- **Ultraviolet Rays**: Used as disinfectants but not commonly associated with physical therapy.
- **Infrared Radiation**: Known for its applications in night vision, heat sensors, and particularly in physical therapy for pain relief and muscle relaxation.

4. **Conclusion**:
- Based on the analysis, the electromagnetic waves detected using a thermopile and used in physical therapy are **Infrared Radiation**.

### Final Answer:
The correct answer is **D. Infrared radiation**.

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