21. light changes its direction when travelling through a new medium because denser mediums have a higher angle of refraction.
        
             
        
        
        
<span>You should deflect the
ball in order to maximize your speed on the skateboard.
Since this creates a larger impulse, you want to deflect the ball. Splitting it
up into catching and throwing the ball may by something you can think of deflecting
the ball. First, you need to catch the ball, which in turn would push you
forward with some speed. (The speed we are talking about should obviously be
equal to option A, where you catch the ball). Now, throw the ball back to him
since these two processes are equal to deflecting the ball. Throwing a mass away
from you would cause or enable you to move even fast.</span>
 
        
             
        
        
        
Yes. Your answer is correct. I hope you do well on the quiz or whatever it is.
        
                    
             
        
        
        
The photocell<span>-- The click rate depends upon the filter selected.</span>