Question

in a vacuum, all electromagnetic waves move:
○ with the same wavelength and differ in their speed and frequency.
○ at the same speed and differ from one another in their wavelength only.
○ at the same speed and differ from one another in their frequency and wavelength.
○ at the same speed and differ from one another in their frequency only.
○ with the same frequency and speed and differ in their wavelength.

Explanation:

In a vacuum, all electromagnetic waves travel at the speed of light (\(c = 3\times10^{8}\space m/s\)). The relationship between speed (\(v\)), frequency (\(f\)), and wavelength (\(\lambda\)) is \(v = f\lambda\). Since \(v = c\) (constant in vacuum), if frequency (\(f\)) changes, wavelength (\(\lambda\)) must also change (\(\lambda=\frac{c}{f}\)). Different electromagnetic waves (e.g., radio waves, visible light, X - rays) have different frequencies and thus different wavelengths.

Answer:

at the same speed and differ from one another in their frequency and wavelength.