Can Water be heated enough to be convert into steam by a magnifying Lens?

Question

So people what the idea?

Answer 1

How much water?  Like a beaker full??  Or just a drop or two?

The whole idea of generating steam is to increase the energy of the water molecules. So you focus the magnifying glass into a beaker of water.  It WILL increase the energy of the water molecules, right in the focus spot.

But you've got the whole beaker full of non-energetic (cool) water, and heat energy flows from hot to cool.  Thus the water under the focus spot stays cool.  This will result in tiny convections of heat energy throughout the beaker.

Now, somewhere I am sure there is some kind of mathematicl formula to predicted how much light energy is being converted to how much heat energy, and you can convert that to calories, and by definition a calorie defines how much energy it takes to raise the temperature of water by one degree.

So you could figure out how long you'd need to hold the magnifying glass over the bearker, to raise the temperature of the water in the beaker to 212 degrees F.

And it is going to be a very long time!  In fact, the water will evaporate before you get it hot enough to boil.

So you have some choices:

Get a bigger magnifying glass.  A really huge one where the focus covers the whole beaker.

Get a brighter light - like a theater spotlight.

Use less water, like a drop or two (or 5 or 10)

I used to do the last one (very tiny puddles of water) when I was a kid.  In fact, outside on a bright sunny day, it will boil before the drop evaporates.

But remember,  Steam itself is invisible!  What you see coming from the tea kettle is actually steam COOLED down to water vapor.  

So using the magnifying glass, you will not get a "cloud" because you simply can't heat ENOUGH water this way. But if you use the smaller drops (a real tiny puddle) you can make it boil, and by definition you can say that since the water was boiling, there must be steam.

Answer 2

Yes. Either, the quantity of water will need to be small or the lens be very large AND you will need and opaque object under the water to heat because the light wont heat the water much because it is as transparent as the glass of the lens.

Answer 3

Definitely. Thats one the methods used in solar power generator where water is evaporated by focussing the rays of the sun onto a water chamber where the temp rises well above 100deg. centi., and the steam is then used to drive the generators.