Ascientsist is testing the effect of light on plants. he takes one plant and sets it on the window sill where it receives light for approximately 10 hours a day. the other plant he places in a dark refridgerator where it receives no light. the plants are the same species, the same size, receive the same water at the same time, the humidity is the same and they receive the same amount of plant food weekly. the plant on the window sill grows much bigger and appears much healthier. what has this scientist proven? explain.