# How to calculate the heat of a metal?

Lets say I leave 100g of copper outside under a convex lens that is 1m squared in surface area (I've been told that 1m2 of sunlight equals 1Kw). How would I figure out the temperature reached for a given amount of copper based on the heat it receives? What about the time it takes to reach that heat? I'm also concerned that a lot of the light would reflect off the copper and not become heat. What's a way around that? Thanks

The above is pretty messy, and you can make a few approximations, since you are dealing with such a small amount of metal and such a large lens. The specific heat capacity of copper is $0.385\,J/(gK)$. Throw in an absorptivity of $0.5$ (taken from here). Assume your optical setup is $10\%$ efficient, so that the sample absorbs $100\,J/s$. This shows us that initially your sample of copper will rise in temperature by about $1K$ a second (or $6K/s$ for a more generous $50\%$ efficient optical setup). Once you start taking other effects into account, the heating rate will be less than this, and will slow down as you reach the maximum temperature.
I forgot to mention that you can't heat the sample beyond about $5500\,K$ (which is the temperature of a black body that best fits the spectrum we receive at sea level). Of course, you need to know what you're doing to get anywhere close to this temperature.