Science Buddies: "Ask an Expert"

So this experiment says that the device built will measure the intensity and duration of light but the procedure looks like you have to time it yourself. The materials don't include a watch though... clarification?

Hi,

The device you built is a light meter that responds to the intensity of light. It does not measure time. It is assumed that everyone has access to a digital watch or clock with a second hand. That’s why the instructions say to have a helper to record the times while you do the manipulations with the water, etc.

Sybee