Diameter of head mirror in ENT is: (A) 20 cm, (B) 22 cm, (C) 10 cm, (D) 26 cm
Answer is C. Head mirror: It is a concave mirror used to reflect light from the Bull's eye lamp onto the pa being examined. It has a focal length of approximately 25 cm. The examiner sees through the hole in the centre of the mirror. Diameter of the mirror is 89 mm (3 1/2 ") and that of the central hole is 19 mm (3/4") Ref: Dhingra 7e pg 427.