how output from a photocell varies with distance from point source of infrared

I am required to design a labratory experiment to investigate how the output from a photocell depends on distance from a point source of infra red radiation.

what procedure should i follow?

what circuit components should i use?

how best would i measure the output of the photocell?

would i measure the current or voltage output?

Er. Do your homework.
If you are required to do it, i would bet you have a textbook that explains it.

As a matter of fact, the way you discripe it it could be either primitiv (well, its r^2 decline for a pointsource), or a trick-question (hopw far infrared? you need higher energy photons then the bandgap of the semiconductor in the detector).

Not enough information.

edit: didnt read the op right...

er, if you are in a position to create such an experiment, you should know what you are doing.
All that stuff is in the standard catalogues for scientific supply. If you dont have the budget, look at the stuff there and buy comparable stuff from normal electronics stores.

You need PSUs, the diods, and some kind of multimeter/instrument.
A wise way to actually build the thing would involve mounting the diodes inside a black PVC tube, with the photodiode being movable (at the end of a stick that has a guide in the endcap, ect).

Your bigger problem will be to shield the photocell from ambient light. Standard photocell extend their range into the near infrared region, they are designed to use the solar light.
You need to move the source with respect to the photocell, and be able to measure the distance.
You need to load the photocell in accordance with its rated power with a resistor, and current flowing trough the resistor or the voltage across it will be directly proportional to each other.
As source, the most common is the infrared LEDs used in remote controls. They have a forward voltage of 1 Volt, and can driven continously at 80 - 90 mA. If you put 6 of them in series to increase the light flux, you use a 82 Ohm resistor and a 12 Volt battery.
But again, your problem will be the external light shielding and the carriage.

Hope this helps.

Anthony