What might explain the contradiction that the Northeast has plenty of mining but is still the poorest region of Brazil in terms of its GDP per capita?

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.