P = 1/f(m) ⇒ f = 1/P = 1/(-4) = -0.25 m = -25 cm. Negative focal length indicates diverging (concave) lens. Memory aid: 'Negative power = concave lens; f(cm) = 100/P(D)'. Direct lens power application frequently tested in competitive exams with sign convention awareness.
Torricelli's Law states that the velocity of efflux of a fluid through a sharp-edged hole at the bottom of a tank filled to a depth 'h' is identical to:
A.The critical velocity for turbulent flow.
B.The velocity of a sound wave in that fluid.
C.The velocity acquired by a freely falling body dropped from height 'h'.
Explanation:
Torricelli's Law is a direct application of Bernoulli's principle. It proves mathematically that the velocity of fluid exiting a small hole (efflux velocity v) is v = sqrt(2gh). This is exactly the same velocity a solid body would acquire if it fell freely under gravity from rest over the same vertical height 'h'.
Explanation:
Wave speed v = fλ = 50 × 0.6 = 30 m/s. Basic wave equation. Ensure consistent units: frequency Hz (s⁻¹), wavelength m. Speed of sound 340 m/s in air, this is slower.
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