What does the electromagnetic spectrum encompass?

The electromagnetic spectrum encompasses the entire frequency range of electromagnetic waves, which includes not only visible light but also a variety of other types of radiation such as radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Each type of electromagnetic radiation corresponds to a different frequency and wavelength, demonstrating a wide range of energy levels.

Understanding the electromagnetic spectrum is crucial in astronomy, as different celestial phenomena emit radiation across these various wavelengths. Telescopes and instruments designed to detect different types of electromagnetic radiation allow astronomers to study objects and conditions in the universe that would be otherwise invisible to the naked eye.

The other options are limited in scope: visible light is only a small part of the spectrum, and citing only radio waves and cosmic rays ignores many other vital components. Sound waves, while they can be discussed in the context of space and astrophysics, do not belong to the electromagnetic spectrum since they require a medium to travel, while electromagnetic waves can propagate through the vacuum of space. Thus, the correct definition of the electromagnetic spectrum is the entire range of electromagnetic waves, making the first option accurate.