Question

air medium A beam of light shines into a transparent medium with parallel surfaces. Part of the beam is reflected back into the air as diagrammed above. (The figure is NOT to scale.) The index of refraction of the medium is 1.5. Which of the following is true? A. θ < θ' and θ < α D. θ > θ' and θ > α Solution: The correct answer is B Because the medium's surfaces are parallel, a perpendicular line drawn to the lower surface of the medium will be parallel to both of the perpendiculars shown in the figure. This means that the angle of incidence at the lower surface will also be α, as will the angle of reflection at the lower surface, and the beam reflecting from the lower surface of the medium will then be a mirror image of the incoming beam, so θ'. θ. Further, because air's index of refraction is about 1.0, Snell's law would show that θ > α. Thus, B is the best answer.

I did not completely understand the explanation or how to get to this answer, I would really appreciate if it could be drawn out and explained more thoroughly. Thanks!

Answer 1

By snail Law n_1 = 1 n_2 = 1.5 n_1 sin theta = n_2 sin alpha 1 times sin theta = 1.5 sin alpha sin theta = 3 sin alpha (1) theta > alpha Ans again Applying snail law From medium to air n_2 times sin alpha = n_1 sin theta' 3/2 sin alpha = sin theta' by equation (1) 3/2 sin alpha = sin theta sin theta = sin theta' theta = theta' option �B� is correct.