A spectrum is produced when light shines through a gas; 

 Atomic emission spectra arise from:
- Electrons dropping from higher energy levels to lower energy levels within the atom.
- Photons (light packets) with specific wavelengths are released, by the formula E = hf
So:             f = ΔE/h  or c/λ = ΔE/h
- The energy levels in an atom are unique to each element on the periodic table. 
- Therefore the wavelength of light emitted can be used to determine which element the light came from.

2.     
How do the lines on the atomic spectrum relate to electron transitions between energy levels?

The lines on the atomic spectrum relate to electron transitions between energy levels.
Emission lines:
- the electron drops an energy level 
- a photon is released 
- resulting in an emission line. 
Absorption lines:
- if the electron absorbs a photon it rises an energy level 
- an absorption line is observed on the spectrum.

 

3.     
Explain the difference between atomic absorption and emission spectra.

The difference between absorption and emission spectra are that:
- absorption lines are where light has been absorbed by the atom
- thus you see a dip in the spectrum
- emission spectra have spikes in the spectra 
- due to atoms releasing photons at those wavelengths.

 

4.     
Describe how the absorption and emission spectra of the gases in the atmosphere give rise to the Greenhouse Effect.

The following needs to be in your answer:
- in what wavelength range the sunlight reaches the earth,
- the absorption of the sunlight
- and the re-radiation as infrared light = HEAT 
- the scattering of the infrared light by the carbon-dioxide 
- how this scattering contributes to the Greenhouse Effect.

5.     
What colour is the light emitted by hydrogen when an electron makes the transition from energy level 5 down to energy level 2? 

ΔE      = E₅ − E₂      
           = 21,0 × 10⁻¹⁹ − 16,3×10⁻¹⁹ J       
           = 4,7 × 10⁻¹⁹ J  
          (MUST GET POSITIVE ANSWER OUT FOR EMISSION)

 
 λ       = hc/ΔE

          = (6,63×10⁻³⁴)(3×10⁸) / 4,7×10⁻¹⁹ 

          = 423 nm               
Colour of light emitted at 423 nm is violet.

6.     
I have a glass tube filled with hydrogen gas and shine white light onto the tube. The spectrum I then measure has an emission line at a wavelength of 474 nm. Between which two energy levels did the transition occur? 

ΔE      = hc / λ

           = (6,63×10⁻³⁴)(3×10⁸ ) / 474×10⁻⁹
           = 4,20×10⁻¹⁹ J         
Transition occurred from E-level 4 to E-level 2.