LED working principle: MCQ with Answer and Explanation

Explanation:
λ = v/f = 350/500 = 0.7 m.

Explanation:
a ∝ -x; magnitude maximum when |x| maximum (extremes). At mean position x=0 ⇒ a=0. Velocity maximum at mean position. Memory aid: 'SHM: a max at extremes, v max at center'. Oscillation concept frequently tested in competitive exams to verify SHM characteristics understanding.

Explanation:
Seismograph detects and records ground motions caused by earthquakes, volcanic activity, or explosions. It measures seismic waves (P-waves, S-waves). Barometer detects pressure changes; hydrophone detects underwater sound; magnetometer detects magnetic fields. Memory tip: 'Seismo = earthquake (like seismology)'. This instrument-application question tests knowledge of geophysical tools, frequently examined in competitive exams. Always associate instrument names with their field of use: seismograph (geology), barometer (meteorology), etc.