Which of the following groups belongs only to the electromagnetic spectrum?

Options

A. alpha rays, beta rays, gamma rays
B. ultra-sonic rays, radio waves, infra red rays
C. gamma rays, cathode rays, X-rays
D. X-rays, radio waves, infra red rays

Explanation

To solve the question, we need to identify which group of rays belongs exclusively to the electromagnetic spectrum. The electromagnetic spectrum includes various types of electromagnetic radiation, which are categorized based on their wavelengths. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Electromagnetic Spectrum
The electromagnetic spectrum consists of a range of electromagnetic waves, which include:
- Cosmic rays
- Gamma rays
- X-rays
- Ultraviolet rays
- Visible light
- Infrared rays
- Microwaves
- Radio waves

### Step 2: Analyze the Given Options
We need to evaluate the options provided to determine which group contains only electromagnetic waves.

1. **Option 1: Alpha rays, Beta rays, Gamma rays**
- Alpha rays and Beta rays are not part of the electromagnetic spectrum; they are particles. Only Gamma rays belong to the spectrum.
- **Conclusion:** Incorrect option.

2. **Option 2: Ultrasonic rays, Radio waves, Infrared waves**
- Ultrasonic rays are sound waves and do not belong to the electromagnetic spectrum. Radio waves and Infrared waves do belong to the spectrum.
- **Conclusion:** Incorrect option.

3. **Option 3: Gamma rays, Cathode rays, X-rays**
- Gamma rays and X-rays are part of the electromagnetic spectrum. However, Cathode rays are streams of electrons and do not belong to the spectrum.
- **Conclusion:** Incorrect option.

4. **Option 4: X-rays, Radio waves, Infrared waves**
- All three of these (X-rays, Radio waves, and Infrared waves) belong to the electromagnetic spectrum.
- **Conclusion:** Correct option.

### Final Answer
The group that belongs only to the electromagnetic spectrum is **Option 4: X-rays, Radio waves, Infrared waves**.

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