Suppose that light travels from one medium where its speed i
     Suppose that light travels from one medium, where its speed is v_1, to another medium, where its speed is v_2. The angle theta_1 is called the angle of incidence and the angle theta_2 is the angle of refraction. Snell\'s Law states that sin theta_1/theta_2 = v_1/v_2. The ratio v_1/v_2 is called the index of refraction. A beam of light travelling in air makes an angle of incidence of 39 degrees on a slab of transparent material, and the refracted beam makes an angle of refraction of 21 degree. Find the index of refraction of the material.  The index of refraction of the material is  (Round to two decimal places as needed.) 
  
  Solution
Index of refrcation = sin(theta1)/sin(theta2) = v1/v2
theta1 = 39 deg ; theta2 = 21 deg
Index of refraction = sin39/sin21 = 1.76

