Why do you believe non- governmental organizations like Invisible Children, Inc. exist? What gaps in the system do they fill?

Which statement is correct? the speed of the light ray is the same in air and medium a. the speed of the light ray is the same in air and medium b. medium a and medium b have different densities because light refracts at different angles. medium a and medium b have the same density because the light ray strikes both at the same angle.