Rough Surface with: Ms = 0.8 HK = 0.4 (a) Find the magnitude of the
force F needed to prevent the
book from sliding down the
rough wall.
F
M = 1.5 kg
600
(b) Find the minimum force F
needed to set the book in
motion up the rough wall with
constant velocity

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