Describe how light is emitted from an atom. a) as protons absorb energy they travel from the nucleus through the atom emitting light along the way. b) the light is emitted when energy from sunlight is absorbed by the atom to excite a neutron into a higher level. c) when the nucleus absorbs sunlight, photons are energized and move to a higher energy level and are then released. d) light is emitted from an atom as an electron falls from an excited state to the ground state releasing a photon.

Answer is: D)Light is emitted from an atom as an electron falls from an excited state to the ground state releasing a photon.

Electrons can jump from one energy level to another, absorbing or emitting electromagnetic radiation with a frequency ν (energy difference of the levels).

When electron jump from higher to lower energy level (shell), it emitting (releasing) energy.

For example, when the electron changes from n=4 (fouth shell) to n=2 (second shell), the photons are emitted.

Albert Einstein (1879-1955) proposed that a beam of light is a collection of discrete wave packets (photons) with energy hν, where h is Planck constant and ν is frequency.

The photons have a characteristic energy proportional to the frequency of the light.

Minimum frequency or the threshold frequency is energy below which no photoelectrons are emitted.  

Above the minimum frequency, energy depends on the frequency of the light, not on the intensity of the light.

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.