For the scientific poster we are supposed to design a poster
This may sound stupid but
How can you design an experiment to measure the rate of photosynthesis in incandescent, halogen, fluorescent and black lights.
Well if you want to measure the rate of photosynthesis, you need to think about what photosynthesis actually produces or uses. In this case, the most obvious is carbon dioxide and oxygen. So I'd recommend measuring via uptake of carbon dioxide or production of oxygen. Although in no light, the opposite occurs, so the easiest way is to measure the change in pH when you add a hydrogen carbonate indicator, which changes colour as carbon dioxide concentration changes.
Therefore, when there is more photosynthesis, less carbon dioxide is produced, which means less is reacted to form carbonic acid, so the pH increases and the indicator turns purple.