In a city grid, each block on the east-west streets is 100 meters long. each block on the north-south streets is 20 meters long. a walker walks 4 blocks west and then 4 blocks south. how much farther did the walker travel than the actual distance between the start and end points?

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