In geometric optics, the power of a lens is defined as the reciprocal of its:
A. Magnification
B. Refractive index
C. Radius of curvature
D. Focal length in meters
Answer: Option D
Solution (By JKSSB Mock Tests)
The power (P) of a lens indicates its converging or diverging ability. It is mathematically defined as the reciprocal of the focal length (f), provided the focal length is measured in meters. The formula is P = 1 / f(in meters). The SI unit of power for a lens is the Diopter (D). A focal length of 0.5m gives a power of 2D.
Explanation:
Power P = V²/R => R = V²/P = 200²/100 = 40000/100 = 400 Ω. Also current I = P/V = 0.5 A, R = V/I = 200/0.5 = 400 Ω. Use P = V²/R for direct calculation.
Explanation:
Pole strength is a property of the magnet; when cut transversely, each piece still has both north and south poles with same pole strength as original. Magnetic moment becomes half because length halves. Each is a complete magnet.
Explanation:
Escape velocity v_e = √(2GM/R), where M is planet mass, R its radius. Thus v_e depends on both M and R. It is independent of the escaping body's mass (as gravitational and inertial mass cancel). Memory tip: 'v_e ∝ √(M/R); larger M or smaller R ⇒ higher escape velocity'. This gravitation formula application is frequently tested in competitive exams. Always recall that escape velocity is a property of the planet, not the projectile. This problem assesses understanding of gravitational potential energy concepts.
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