Speed of electromagnetic waves is the same

Options

A. for all wavelengths
B. in all media
C. for all intensities
D. for all frequencies .

Answer

To solve the question regarding the speed of electromagnetic waves, we need to analyze the options provided and understand the underlying physics principles.

### Step-by-Step Solution:

1. **Understand the Speed of Electromagnetic Waves**:
The speed of electromagnetic waves in a vacuum is denoted by \( c \) and is given by the equation:
\[ c = \nu \lambda \]
where \( \nu \) is the frequency and \( \lambda \) is the wavelength.

2. **Analyze the Options**:
- **Option 1**: "For all wavelengths" - This implies that the speed remains constant regardless of the wavelength. However, since \( c \) is a product of frequency and wavelength, changing one will affect the other, thus this option is incorrect.
- **Option 2**: "In all media" - The speed of electromagnetic waves is not the same in all media. It is maximum in a vacuum and decreases in other media. Therefore, this option is also incorrect.
- **Option 3**: "For all intensities" - The intensity of an electromagnetic wave is related to the square of the electric field and does not affect the speed of the wave. Thus, this option is correct.
- **Option 4**: "For all frequencies" - Similar to option 1, since frequency and wavelength are inversely related, changing the frequency will change the wavelength, and thus the speed will not remain constant. Therefore, this option is incorrect.

3. **Conclusion**:
After analyzing all the options, we find that the only correct statement is that the speed of electromagnetic waves is constant for all intensities. Therefore, the correct answer is:
\[ \text{Option 3: For all intensities} \]