What does voltage measure?

Which statement is true for light passing into a medium that is more optically dense than the first medium through which it past

Jason is a body builder. despite being more fit, he weighs more than his brother ryan, who is the same height. which is a possible reason? a. jason has more muscle mass than ryan does. b. jason has more body fat than ryan does. c. jason has more muscle mass and body fat than ryan does d. jason has less body fat than ryan does.

In what direction does the medium move relative to the direction of the wave? explain.