Electric field due to point charge: E ∝ MCQ with Answer and Explanation

Explanation:
Endoscopes consist of bundles of flexible optical fibers. Light introduced at one end is trapped inside the fiber core because it repeatedly strikes the boundary at an angle greater than the critical angle. This Total Internal Reflection allows light and visual images to be transmitted through complex, curving paths inside the body.

Explanation:
For low Earth orbit (r ≈ R_earth), orbital period T = 2π√(r³/GM). Using g = GM/R², T = 2π√(R/g). With R = 6.4×10⁶ m, g = 9.8 m/s², T ≈ 2×3.14×√(6.4e6/9.8) ≈ 6.28×√(653061) ≈ 6.28×808 ≈ 5076 s ≈ 84.6 minutes. Memory aid: 'Low orbit period ≈ 84 min; geostationary = 24 hours'. This standard result is frequently tested in competitive exams. Always recall that period increases with orbital radius; competitive exams often compare low orbit vs geostationary periods.

Explanation:
d = (v×t)/2 = (340×0.5)/2 = 170/2 = 85 m. Minimum distance for echo perception is about 17 m. Remember divide by 2 for one-way distance.