Which term designates the entire range of electromagnetic waves arranged in order of their frequencies?

• A. Spectrum
• B. Photon
• C. Antenna
• D. Laser

Answer: (A)

The term for the entire range of electromagnetic waves arranged in order of their frequencies is the electromagnetic spectrum. This spectrum spans from radio waves up through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, organized by increasing frequency (or decreasing wavelength). The word spectrum conveys a continuous range rather than a single packet of energy, which fits the idea of all possible EM waves together. A photon is a single quantum of light, not the whole range. An antenna is a device used to radiate or receive EM waves, not a descriptor for the range. A laser is a source that emits light—often at a specific, narrow frequency band—rather than the entire spectrum. While the spectrum can describe the distribution of frequencies present in a signal, its broad, standard meaning is the full set of EM waves.