can you lend me your brains please ? as physics,aqa

You know that a photont completely gives up it's energy when it meets an electron.However, electric forces must be overcome for the electron to be released from the metal. This minimum amount of energy required is called the work function.

If the photon can only completely give up it's energy then the photon's energy minus the work function must be the e;ectrons kinetic energy.

You know that the kinetic cnergy KE = 1/2mv^2.

You know the kinetic energy and the mass .. just sub to find the maximum speed.

(it is the maximum because the phootn can sometimes travel deeper into the metal and then if it hits an electron, weven moe energy is required.).

ahh...thnks. much appreciated <3
perhaps i need to re-read the txtbook.
the maximum speed bit threw me off.
& i dunno now if i have such a sound grasp on what exactly photons do ...

Sorry, you want to know what they do. My mistake. Well, they aren't a particle in the conventional sense, and their relativisic properties also deny us imagining (or should I say specifying) it's approximate location even more so than a normal 'particle' who only obeys Heisenberg;s uncertainty principle. You should not think of it as being a soley particla nature. You should think of a probability wave near it (see Heisesnberg's uncertainty and relativistic effects). Also, you can't specify it's path (If you are interested as to why this is so, read Feynman's path integral article on wiki). It is pure enrgy and not made up of anything smaller. You can't imagine how it travels. All a photon is a way of energy being transefeered from one place to another.