Attach a light sensor to a servo (use just a tiny bit of hot glue). Create three versions of a light detector / follower:

1. Sweep the servo from one end of its range to the other, and print out via the Serial monitor the minimum value seen (that's the brightest point), and at what angle it was found. Repeat forever.

2. Create an enhanced version of the above where after the servo completes its sweep, it stops and moves to the brightest point it had seen. Delay a moment, then repeat: sweep again, then after sweeping, point to the brightest spot. Repeat forever.

3. As an alternative approach, have the servo with the photocell on it continually sweep back and forth, and add a second servo (placed on the table as close as you reasonably can to the first servo) to point near the brightest spot. The first servo should never stop sweeping; the second servo should move when it can to update its estimate as to where the light source is. There are admittedly some geometry issues in getting this perfect, since the two servos aren't at quite the same location; just get it roughly right.

If you managed to get this done sooner than expected and are looking for optional bonus work: try to modify one of the above to add some sort of artificial intelligence to it. Perhaps you might try to have the sweeping servo be smarter about trying to locate the light instead of just using fixed sweeps across its entire range.