15. A level glass-bottomed tank contains liquid as shown. A beam of light is incident at angle θ on the upper liquid surface. Select the largest value for θ in degrees given below which permits this light to leave through the bottom glass-air surface.

(A) 89
(B) 56
(C) 48
(D) 38
(E) 21.
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統計: 尚無統計資料
統計: 尚無統計資料