The prefix 'femto' in SI units represents a factor of: MCQ with Answer and Explanation

Explanation:
Seismograph records seismic waves. Richter scale quantifies magnitude.

Explanation:
T ∝ 1/√g, g_moon < g_earth, so T increases.

Explanation:
This is the Doppler effect: when source moves toward observer, wavefronts compress, decreasing wavelength, thus increasing apparent frequency (f' = f·v/(v - v_s), where v is sound speed, v_s source speed). Conversely, receding source decreases frequency. This applies to all waves (light, sound). Memory aid: 'Approaching = higher pitch (frequency); Receding = lower pitch'. Competitive exams often test qualitative understanding before formula application. Always identify motion direction relative to observer for sign conventions in numerical problems.