If the average density of planet x is equal to earth's average density, ρe, what is the ratio of rx/re, where re is the mean radius of earth

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. this works through a process known as multiphoton absorption. in this process, several photons are absorbed at the same time. if very intense light whose photons carry 2ev of energy is shined onto a material with a band gap of 4ev, that light can be absorbed through two-photon absorption, because two photons have the right amount of energy to bridge the band gap. what is the minimum number of photons of 800-nm light that are needed to equal or exceed the band gap of fused silica glass

Positrons are spontaneously emitted from the nuclei of

Lightning is an example of what phenomenon? a release of a large amount of energyan absorption of a large amount of energya natural electric circuita natural electric current