The working of an optical fibre is based on MCQ with Answer and Explanation

Explanation:
d = (v×t)/2 = (340×0.1)/2 = 17 m.

Explanation:
After n half-lives, activity reduces to (1/2)ⁿ of initial. Set (1/2)ⁿ = 1/16 ⇒ (1/2)ⁿ = (1/2)⁴ ⇒ n = 4 half-lives. Thus time = 4 × half-life. Memory aid: '1/2ⁿ remaining after n half-lives; 1/16 = 1/2⁴ ⇒ 4 half-lives'. This radioactivity calculation is frequently tested in competitive exams. Always express fraction as power of 1/2 to find half-life count. This problem assesses understanding of exponential decay without heavy computation.

Explanation:
Average speed = total distance / total time = d / ( (d/2)/v1 + (d/2)/v2 ) = 2v1v2/(v1+v2).