Physics P1 - Collisions of electrons with atoms

How do electrons exist in an atom?

In discrete energy levels.

How do electrons gain energy?

From collisions with free electrons.

What is excitation?

Energy from a collision causes an electron to move up an energy level.

What is ionisation?

When an electron gains enough energy to be removed from the atom entirely.

What is the ionisation energy?

It is the minimum energy required for an electron to be released from an atom.

What happens when an electron becomes excited?

It will quickly return to its original energy level, and release the energy it gained.

How do electrons release energy?

In the form of a photon.

What is a practical use of excitation?

A fluorescent tube.

What do fluorescent tubes produce?

Light

What is in a fluorescent tube?

Mercury vapour.

What happens to the mercury vapour in a fluorescent tube when a high voltage is applied across it?

Free electrons are accelerated through the tube.

What is caused by ionised mercury atoms in a tube?

More free electrons are released.

What happens when electrons de-excite in a tube?

They release photons, most of which are in the UV range.

What absorbs the photons in a tube?

Phosphorous coating, which then causes the electrons to release photons of light.

What is an electron volt?

It is defined as the energy gained by one electron when passing through a potential difference of 1 volt.