S-Cool Revision Summary

S-Cool Revision Summary

Electrons, protons, α -particles can be diffracted! That's a wave thing!

de Broglie found the equivalent (de Broglie) wavelength for particles:

λ = h/p

where p = momentum of the particle.

E-M radiation:-

- propagates as a wave.

- interacts with surfaces as a particle.

Look at the Sun (Don't actually look at it though!) It doesn't have a complete white light spectrum. There are tiny gaps (lines) of no light! This light has been absorbed by gas around the Sun. Why are only certain lines (which relate to certain frequencies) absorbed?

The Answer:

Electrons can only exist in discrete energy levels around nuclei.

When jumping from low to high levels, they absorb energy in lumps.

When jumping from high to low levels, they emit energy in lumps.

The lumps have energy value calculated using:

h f = E1 - E2

The lines on the spectra are the frequencies of light that exactly match the energy required to make the jumps between energy levels.

Dark lines on coloured background.

Lines of colour on a dark background.

E = hf

λ = h/p

h f = E1 - E2

h = Planck's constant, Js

f = frequency, Hz

λ =wavelength, m