BPSC – Combined Competitive Examination · প্রশ্ন 127
The focal length of a plane mirror is:
উত্তর দেখান ও ব্যাখ্যা
উত্তর: (D) Infinity
ব্যাখ্যা
A plane mirror can be seen as a sphere of infinite radius, so its focal length is infinite.
- (A) ভুল
Wrong: a plane mirror has no finite focus.
- (B) ভুল
Wrong: a plane mirror has no finite focus.
- (C) ভুল
Wrong: a plane mirror has no finite focus.
- (D) সঠিক
Correct: its radius of curvature is infinite, so f = R/2 is infinite.