If the frequency of wave is 400 Hz and its
wavelength is 2.5 m, what is the velocity?
a 3000 km/s
b 100 m/s
C 10000 m/s
d 1000 m/s

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

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?