Good physics topic for my in class presentation

[rspandher]

can somebody please suggest me a good physics topic for my in class presentation. i am in third semester college physics and we have to built something using physics. there is so much in physics. i can not figure what to do for the presentation. somebody please give me a good advice on this

 

[arcnets]

Hi rspandher,
if you can think of so many things, why not pick the most interesting one? There must be, I think, some experiments which have been fascinating to you for a long time, but you never exactly figured out how they work. Or things that have been discussed intensely among students with no final conclusion. Being 3rd semester, I imagine something mechanical, electromagnetic or optical would be good - is it the same in India? Also, since you are to *build* something, electronics is maybe a good idea...

 

[rspandher]

project

thankque arcnets for giving a advice on the project. yea i want to to do something more with the photoelectric effect but i don't know whatto do with it. are there any applications of photoelectric effect which i could show in the class using easily available material.

 

[arcnets]

Yes. It's called the Hallwachs experiment. All you need is an ordinary electroscope plus a zinc plate to fix on top. Now charge the electroscope positive, and expose the zinc plate to light. Nothing will happen. But charge negative, and the electroscope will discharge quickly when zinc plate is exposed to light. This is because electrons get kicked out by photons. Note, the zinc plate has to be polished properly, prior to each experiment. Since zinc easily builds up oxides on the surface which spoil the effect.
The next step you show is, it won't work when the light falls thru glass. Since only the UV component produces the effect, and glass blocks that. Good luck!