Which statement about the visible spectrum is true?

• A. It spans wavelengths between 400 and 700 nanometers.
• B. It lies entirely outside the electromagnetic spectrum.
• C. It has the longest wavelength in the electromagnetic spectrum.
• D. It is the lowest energy form of electromagnetic radiation.

Answer: (A)

Visible light is the part of the electromagnetic spectrum that humans can detect with our eyes, and it is defined by wavelengths in a range roughly from 400 to 700 nanometers. Within this band, the different wavelengths correspond to the colors we perceive, from violet near 400 nm to red near 700 nm. Because energy per photon scales inversely with wavelength (shorter wavelengths have higher energy), the visible range sits between ultraviolet (shorter wavelengths) and infrared (longer wavelengths) on the spectrum. It’s not outside the electromagnetic spectrum, it does not have the longest wavelengths (that distinction goes to longer-wavelength infrared or beyond), and it isn’t the lowest-energy region of EM radiation (regions like radio waves have lower energy photons). The 400–700 nm range is the standard way we define the visible spectrum, making that statement true.