When light in medium 1 is reflected from the surface of medium 2 ...

[wenmo]

When light in medium 1 is reflected from the surface of medium 2 with the indices of refraction of the media being n1 and n2 respectively, the reflected light has a phase difference of 180 if
 
  A)
 
  n1 > 3 n2.
  B)
 
  n1 = n2.
  C)
 
  n1 < n2.
  D)
 
  n1 > n2.
  E)
 
  n1 > 2 n2.

Question 2

A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37.0 above the horizontal. The mass of the box and the books is 40.0 kg. (a) Draw the free-body diagram for the box.
 
  (b) Calculate the acceleration of the box. (c) Calculate the normal force acting on the box.

[mk6555]

Answer to Question 1

C

Answer to Question 2

(a) The box is acted on by the force of gravity which points toward the center of the earth. The normal force is directed toward the box perpendicular to the surface of the floor. The pulling force is directed away from the box at an angle 37.0 degrees above the horizontal.
(b) 2.00 m/s2
(c) 332 N