A ray of light strikes a flat block of glass (n=1.5) of thickness 2.0 cm at an angle of 30 degrees with the normal. Find the distance the light is shifted. I found the angle of refraction to be 19.471 degrees. I figured I could find the horizontal distance travelled by rays going through at 30 and 19.471 degrees using tan(theta) = d/2. Then I subtracted one distance from the other, and I get .446 cm, when, according to the book, I should get 3.88 mm. What am I doing wrong?