Final answer:
The velocity of a radio wave is the same as the velocity of light in a vacuum which is 3×10⁸ m/s. Sodium vapor lamps emit visible light, while helium lasers emit visible red light.
Step-by-step explanation:
The velocity of a radio wave is the same as the velocity of light in a vacuum, which is approximately 3×10⁸ m/s. This applies to all electromagnetic waves, including radio waves. So, the velocity of a microwave is also approximately 3×10⁸ m/s.
A sodium vapor lamp giving off yellow light emits a type of electromagnetic wave known as visible light. Visible light falls within the range of wavelengths in the electromagnetic spectrum, and yellow light specifically has a wavelength between 570 and 590 nanometers.
A helium laser emits visible red light. Red light has a longer wavelength than yellow light, typically ranging from 620 to 750 nanometers.