A Level Physics Practice Exam

What term describes the outcome when an atom's electron is excited by incoming energy?

1. Continuous spectrum

2. Line emission spectrum

3. Absorption spectrum

4. Black body radiation

The correct answer is: Line emission spectrum

When an atom's electron absorbs energy, it can become excited and move to a higher energy level. This process can lead to the emission of light when the electron subsequently returns to its original or lower energy level. The specific wavelengths of light emitted correspond to the differences in energy levels, resulting in distinct lines in the spectrum known as the line emission spectrum. Each line in this spectrum represents a specific transition between energy levels, allowing us to identify the elements present. While the line emission spectrum pertains to the light emitted when electrons fall back to lower energy levels, the other options relate to different phenomena. For instance, a continuous spectrum refers to a range of wavelengths emitted by a hot solid or gas under high pressure. The absorption spectrum describes the wavelengths absorbed by an atom or molecule when electrons are excited, showing darker lines on the continuous spectrum. Black body radiation describes the electromagnetic radiation emitted by an idealized perfect emitter at thermal equilibrium, which is a different concept altogether.