I came here just now to ask a question very similar to yours,
but my question might be your answer. I want to do a Science
Fair project to measure the "size" of a photon. I have no idea
whether such a thing is possible. The "size" of photons seems
not to be well-defined. They are often considered as pointlike,
but are also considered as thousands of wavelengths long.
I'm going to ask how such a measurement could be done.
If you are interested in this question and can come up with a
way to try to answer it, I would be thrilled if you took it on.
Do you have a sponsor or a guide who can help you in person?
I think it really helps to have someone who you can talk with
and show what you are working on. I saw an 11th grader's
Science Fair project on aerodynamics that was beautifully done,
but he made a very silly mistake in how air flows around the fins
of a model rocket, so that his careful observations were pretty
much worthless. Somebody should have caught that mistake
very early on and helped him understand how it works. That
means frequently explaining what you are trying to do and why
you are trying to do it, and getting feedback from at least one
person who can follow your explanations.
-- Jeff, in Minneapolis