Longest pa of the optic nerve is
High-Yield Explanation
The optic nerve is about 47- 50 mm in length and can be divided into 4 pas : intraocular (1mm), intraorbital (30mm), intracanalicular (6-9mm) and intracranial (10mm). Refer comprehensive ophthalmology 6th edition , A K Khurana , page no. 310.