I am going to give up Pilsners.
— The Lenten sacrifice made by an engineer. His wife wanted him to give up beer entirely, but that was too much to ask.
An article on Stumbleupon called "8 shocking things we learned from Stephen Hawking's book" considered the following statement from The Grand Design shocking.
A 1-watt night-light emits a billion billion photons each second.
We can easily compute this number after making a few assumptions:
- We are talking about an incandescent bulb (Figure 1).
- The incandescent bulb is ~4% efficient – this means that 4% of the input power goes into making visible light.
- We will only be considering photons in the range of human vision. There are actually many more photons emitted with wavelengths outside the range of human vision.
Figure 2 shows my calculations.
Easy enough calculation. However, I never have seen a 1 W nightlight bulb. I think the smallest I have seen is 7 W.