Visible light travels more slowly through an optically dense medium than through a vacuum. A possible explanation for this could be that the light: A is absorbed and re-emitted by the atomic structure of the optically dense medium. B is absorbed and re-emitted by the nucleus of the material in the optically dense medium. C bounces around randomly inside of the optically dense medium before emerging. D loses amplitude as it passes through the optically dense medium. Solution: The correct answer is A.

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)