The absorption spectrum of helium has a black vertical line at a wavelength of 502 nm. What can you conclude about atoms of helium? A. They emit photons with a wavelength of 502 nm.
B. They do not emit photons with a wavelength of 502 nm.
C. They emit photons with a wavelength that is shifted slightly above 502 nm.
D. They emit photons with a wavelength that is shifted below 502nm.