Question

1. Explain why an element only emits certain colors (wavelengths) of light instead of a full rainbow

2. What color of light is emitted by a photon with an energy of 3.40 x 10-19 J? What is the
frequency of this photon? Show all work!

Answer 1

1.

When sunlight passes through a prism, it spreads into a continous spectrum or a Rainbow. When light from Hydrogen (glowing) is passed through the same prism we can observe only four lines of coloured light that are discontinous. This discontinous spectrum of four coloured lines is called the Atomic or Emission Spectrum of Hydrogen. Emission Spectrum is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states.

E = hV

E - Energy of the photon

h - Planck's Constant

V - Frequency

Since an atom transition can emit on a specific amount of energy when excited (burnt/incident radiation) the emission spectra are specific for specific substances.

2.

E = 3.4*10^-19J

h = 6.63 x 10^-34 J.s

V = E/h = 0.513*10¹⁵ s^-1 This is the frequency of the Photon.