The expectrum of visible light is what we call all wavelenghts visible to human beings, we can se an expectrum from 400 nM to 750 nM, the 400 are the violets and the 700 are the reds, everything over 750 has longer wavelength than the visible light, that would be Radiowaves, with a wave length of 1m, Microwaves with a length range form 1 milimiter to a meter, and Infrared that are just above the 700 nM.
A. The amount of work increases. Imagine you are pushing a box on a flat surface. Now imagine pushing it up a steep hill. It gets harder and that's how I remember this. Hope this helps.
Think of it this way: If you test only one variable then you know that the difference in the experimental and control setup is that one independent variable. If you test more than one you will not know which one made the difference. Hope this helps :)
