This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Ophthalmology
Critical angle of air corneal interface- 
Select and explain. 
A. 36 degree, B. 46 degree, C. 56 degree, D. 66 degree
B: 46 degree
Answer: B: 46 degree 
Explanation: *Critical angle of cornea-air interface is, approximately 46o. Ref: Khurana: Theory and practice of refraction 7th/e p.99