Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: Lights, Camera, Tomato!?

Learn more physics!

Most recent answer: 10/22/2007
Q:
Does the type of light effect the growth rate of a tomato?
- Johnathon Currid (age 15)
MCW, Welcome, Minnesota, USA
A:
Johnathon -

The most important thing for how the plant will grow is how much light it gets. Plants use special molecules called chlorophyll to turn light energy into chemical energy that they can use. The more of this energy that the plant gets, the more it will grow. So, if you use a really bright light, you will probably find that your plants will grow more than if you use a dim one.

But there's more to it than just this. The chlorophyll that the plant uses to get energy is green (hence the fact that most plants are green). When something looks like it is a certain color, it's actually because all the light of that color that hits it bounces right back off. The white light from the sun is actually a mixture of all the different colors of light (this is why separating the colors gives you a rainbow). When the white light hits the leaves of the plant, the chlorophyll absorbs all the colors except for green and the green bounces right off. So I'd bet that if you tried this experiment at home, you might find that the plant doesn't grow very well under a green light, but that it does fine with blue or yellow. Since I'm not sure about this, please try it and let me know what happens.

-Tamara

(published on 10/22/2007)

Follow-up on this answer.