The speed of light in a medium is measured to be 138,274,140 m/s, what is the refraction index for the medium?

Assuming weightless pulleys and 100% efficiency, what is the minimum input force required to lift a 120 n weight using a single fixed pulley?

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

Use the right-hand rule for magnetic force to determine the charge on the moving particle. this is a charge.