Question

multiple choice question
which of these describes an atomic emission spectrum?
the frequencies of the em waves emitted by an element
the wavelengths of light reflected by an element
the energy levels of the electrons in an element

Explanation:

An atomic emission spectrum is formed when electrons in an atom return to lower energy levels and emit electromagnetic (EM) waves. It represents the frequencies (or wavelengths, since \(c = \lambda
u\)) of these emitted EM waves. Light reflection is not related to emission spectra. Energy levels of electrons are the cause of emission but not the description of the spectrum itself. The spectrum shows the frequencies (or wavelengths) of the emitted EM waves. So, the description of an atomic emission spectrum is about the frequencies of the EM waves emitted by an element (as frequency and wavelength are related by \(c=\lambda
u\), and emission spectra can be presented in terms of either, but the first option is a more direct description in terms of a property of the EM waves emitted).

Answer:

the frequencies of the EM waves emitted by an element