The heat (energy) needed to raise the temperature of the water is given by
The wavelength of the radiation of the oven is
, so the energy of a single photon of this radiation is
So, the number of photons required to heat the water is the total energy absorbed by the water divided by the energy of a single photon:
photons
A light-year is a unit of distance.
The definition of a light-year is the distance light travels in one year.
There is no such thing as an AC Generator, if its a generator, its DC. I think you are talking about an AC Alternator, in which case the answer would be -wrong answer, deleted-
If you're referring to the different colors that usually occur at the tip of missles, rockets and some other aircraft, it either a) signifies the end of a particular plate of metal, fabricated specifically to be for the nose. Sometimes these can even be a different alloy or metal all together. or b) this shows where the curved surface begins, so in the case of damage or imperfections due to wear, they can be repaired and measured more easily. The shape of the nose is extremely important for smooth flight, and a dent or bump formed on it can make the aircraft unstable. If you can measure from where the curve starts by the difference in color, it makes repairing or re-fabricating the part much easier. Many of these curves aren't as simple as they appear.
