Sam did an experiment. He boiled water in a teapot and saw vapor coming out. When he placed a cold plate in contact with the vapor it formed droplets of water.? Can you imagine what was that process and Why did he observe this?

If you chip a tooth, most likely you will go to the dentist to have the missing material filled in. currently the material used to fill in teeth is a polymer that is flexible when put in, yet is hardened to the strength of a tooth after irradiation with blue light at a wavelength of 461 nm. what is the energy in joules for a photon of light at this wavelength?