What equation can be used to calculate either wavelength, frequency or speed?

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.

Ionic compounds can be readily dissolved in water because the high dielectric constant of water screens and decreases the force between the oppositely charged ions.