Emission And Absorption Spectra

Question 1

Describe the absorption spectra

Answer 1

When white light shines through gaseous atoms, photons of certain energy may be absorbed by atoms causing an electron to move from a lower energy level to a higher one- it is said to be in an excited state. This means that light of a frequency corresponding to the energy of the photon will be removed. Therefore when the light is examined by a spectrometer, the electron transitions will appear as dark lines against a bright background

Question 2

Describe emission spectra

Answer 2

Source of energy removed
Electrons fall
Energy lost as a packet of energy- quantum of energy
Corresponds to electromagnetic radiation of specific frequency
Coloured lines on dark background

Question 3

Describe the visible emission spectrum of hydrogen

Answer 3

A series of lines converging as the energy increases. The lines are caused by excited electrons dropping to second energy level.

Question 4

Balmer series

Answer 4

N=2

Question 5

Lyman series

Answer 5

N=1

Question 6

What is the convergence limit?

Answer 6

When the spectral lines become so close together they have a continuous band of radiation so separate lines cannot be distinguished

Question 7

Finding the ionisation energy of hydrogen

Answer 7

Find the frequency of the convergence limit using the lyman series and the equation E=hf