Which wavelengths are observed in the emission spectrum of an atom?

• A. Only ultraviolet wavelengths
• B. All possible wavelengths across the electromagnetic spectrum
• C. Only infrared wavelengths
• D. Only specific discrete wavelengths corresponding to electronic transitions

Answer: (D)

Verified step by step guidance

1. Understand that the emission spectrum of an atom arises from electrons transitioning between discrete energy levels within the atom.
2. Recall that when an electron drops from a higher energy level to a lower one, it emits a photon with energy equal to the difference between those two levels.
3. Use the relationship between energy and wavelength of the emitted photon, given by the equation \(E = \frac{hc}{\lambda}\), where \(E\) is energy, \(h\) is Planck's constant, \(c\) is the speed of light, and \(\lambda\) is the wavelength.
4. Recognize that because the energy levels in an atom are quantized, only specific energy differences (and thus specific wavelengths) are possible, leading to discrete lines in the emission spectrum.
5. Conclude that the emission spectrum consists of only specific discrete wavelengths corresponding to these electronic transitions, not a continuous range or all wavelengths across the electromagnetic spectrum.