What is 80% as a ratio

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?

Which of these features are formed when hot groundwater is forced out through cracks in the earth's surface?

Write a balanced equation showing the formation of copper (ii) nitrite from its elements