Why is rate of photosynthesis more during a bright sunny day as compared to cloudy day ?

One of the important requirements of photosynthesis is sunlight. Rate of photosynthesis depends on the quantity of sulight available. On a cloudy day, very little sunlight is available. So the rate of photosynthesis will be very low. On the other hand, a bright sunny day will provide bright sunlight, leading to a high rate of photosynthesis.