The coefficient of performance of a refrigerator is defined as: MCQ with Answer and Explanation

Explanation:
Geostationary satellites orbit in Earth's equatorial plane with period matching Earth's rotation period (24 hours), so they appear stationary relative to ground. Orbital radius is about 42,000 km from Earth's center. Memory tip: 'Geostationary: T=24 h, equatorial orbit, fixed position; used for communication/weather satellites'. This standard result is frequently tested in competitive exams. Always recall that geostationary is a special case of geosynchronous (same period) with zero inclination; competitive exams often compare low orbit (84 min) vs geostationary (24 h) periods.

Explanation:
Object between P and F of concave mirror gives virtual, erect, magnified image behind mirror. Used in shaving mirror, dentist mirror. Ray diagram shows diverging rays appearing to come from behind.

Explanation:
Law of reflection: angle of incidence = angle of reflection, both measured from normal. So 30°. If angle with mirror is given, convert to normal. Always equal for smooth surfaces.