The frequency of AC mains in India is 50 Hz. The time period is MCQ with Answer and Explanation

Explanation:
Angular momentum L = r × p. Position r has [L], linear momentum p = mv has [MLT⁻¹], so L has [L][MLT⁻¹] = [ML²T⁻¹]. This matches Planck's constant dimensions. Option A is linear momentum; C is energy/torque; D is dimensionless. Memory aid: 'Angular momentum: [ML²T⁻¹]; same as action quantities'. This dimensional analysis question tests ability to derive formulas, crucial for competitive exams. Always break down compound quantities into fundamental dimensions (M, L, T) for verification and problem-solving.

Explanation:
A geostationary satellite must appear stationary to an observer on the Earth's surface. To achieve this, it must orbit in the exact equatorial plane and strictly follow the Earth's rotation. Since the Earth rotates on its axis from West to East, the geostationary satellite must also orbit from West to East.

Explanation:
RADAR uses microwaves (short wavelength radio waves). Often classified as microwaves.