A lens only redirects the light, so that all of the energy that hits it comes together at a spot. This doesn't change the amount of energy that is involved. A lens doesn't make energy -- it only concentrates it.

There is a right place to put a lens relative to a viewing screen, so that all the light that comes from one place in a light source ends up one place on the screen. The sequence of pictures below illustrates this.

	a large dim spot
	a smaller, brighter spot
	A very small, very bright spot
	Oops! Too close!

The light source in this sequence was a distant light bulb. When the light source is closer, the lens needs to be a little further away from the screen; and instead of a spot of light, you may get a picture of the light bulb!

Do the activities Does light carry energy and Can light energy be concentrated in the manual (Radiation #1 and #2).

Check the box when you are done:   About convective and radiative heat transfer