Correct Answer:
A. Same for all intensities
The correct answer is Same for all intensities.
- Explanation: The speed of electromagnetic waves, including light, in a vacuum is a fundamental physical constant, denoted as 'c'. This speed is approximately 299,792,458 meters per second and is independent of the wave's intensity, frequency, or wavelength.
- Why other options are false:
- B & C (Faster/Lower for higher intensities): Intensity relates to the amplitude of the wave, which affects its energy, but not its speed in a vacuum.
- D (Dependent on frequency): While frequency and wavelength are inversely related (c = fλ), the speed 'c' itself is constant and does not depend on the frequency of the wave.