Answer: 41.8 degrees.
- A 38.6 degrees
- B 41.8 degrees
- C 48.2 degrees
- D 60 degrees
Correct answer: B. 41.8 degrees
Explanation: For TIR at curved surface (glass-air), critical angle = sin<sup>-1</sup>(1/1.5) = sin<sup>-1</sup>(0.667) = 41.8 degrees. The angle of incidence at flat face that produces this must be calculated, but if ray hits curved surface at 41.8 degrees grazing, minimum incidence at flat face = 41.8 degrees.
Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.
Concept context
Reflection, refraction, lenses, mirrors, total internal reflection.