Question

which of the following best describes the production of unique spectral lines by the elements?
a. when energy is added to a sample of an element, the samples mass increases, because of the mass - energy equivalence, and the energy is then reemitted at only those frequencies that correspond to the original mass.
b. when white light shines on an element, the reflected light is limited to certain wavelengths and frequencies, which correspond to the spectral lines.
c. when an element interacts with electromagnetic radiation, it absorbs radiation in all wavelengths and reemits it with each wavelength separated from the others.
d. a heated sample of an element emits light of only certain allowed energies, which correspond to the spectral lines for that element.

Explanation:

When an element is heated, its electrons gain energy and jump to higher - energy levels. When these electrons return to lower - energy levels, they emit photons of specific energies. The energy of a photon is related to its frequency and wavelength by $E = h
u=\frac{hc}{\lambda}$, where $h$ is Planck's constant, $
u$ is frequency, $c$ is the speed of light, and $\lambda$ is wavelength. These specific energies correspond to the unique spectral lines of the element. Option A is incorrect because mass - energy equivalence is not related to spectral line production in this context. Option B is incorrect as it's not about reflection in the context of spectral line production. Option C is incorrect because elements do not absorb radiation in all wavelengths but only at specific ones corresponding to energy level differences.

Answer:

D. A heated sample of an element emits light of only certain allowed energies, which correspond to the spectral lines for that element