We can use the equation of motion: s = ut + 1/2 x at² Both the velocity and acceleration are downwards so we'll consider the downward direction positive 30 = 8t + 4.91t² 4.91t² + 8t - 30 = 0 Solving the quadratic: t = 1.79 s; t = -3.42 s Negative time is not possible so second value discarded. Time taken = 1.79 seconds
The answer to this is A. this is because, refraction with a light or sound wave changing its direction involve propagation,(in which propagation is the change in direction of a light or sound wave)
