Which physical quantity has the same value for waves belonging to the different parts of the electromagnetic spectrum?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Electromagnetic Spectrum**: The electromagnetic spectrum includes a variety of waves, such as radio waves, microwaves, infrared, visible light, ultraviolet (UV) rays, X-rays, and gamma rays. Each of these waves has different properties, including wavelength and frequency.

2. **Identifying the Physical Quantities**: For electromagnetic waves, two key physical quantities are wavelength and speed. Wavelength varies significantly across the spectrum, while speed is a fundamental property of all electromagnetic waves.

3. **Analyzing Wavelength**: In the question, we are given specific examples: a microwave with a wavelength of 1 mm and UV radiation with a wavelength of 1600 Å (angstroms). Clearly, these two wavelengths are different, indicating that wavelength cannot be the same across different types of electromagnetic waves.

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