ایک کیلوری کتنے جولز کے برابر ہے؟
A. 4185 joules
B. 4286 joules
C. 4285 joules
D. 4184 joules
Explanation
1 kilocalorie (kcal) = 4184 joules , commonly used in food energy.
1 calorie (cal) = 4.184 joules , so 1000 cal = 4184 J.
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A. None of these
B. 2.314
C. 8.314 × 10⁷
D. 8.314 × 10⁷
Explanation
The gas constant R in ergs mol⁻¹ K⁻¹ is 8.314 × 10⁷ . It is derived from the SI value 8.314 J mol⁻¹ K⁻¹ , where 1 J = 10⁷ ergs. Show/Hide Explanation
روشنی کی رفتار کا تعین سب سے پہلے کس نےکیا تھا۔
A. Galilee
B. Remer
C. Albert Einstein
D. Ole Romer
Explanation
Ole Rømer , an astronomer from Denmark made the first quantitative measurements of the speed of light in 1676 .
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ایس آئی یونٹوں میں ، طول موج کی اکائی ______ ہے؟
A. A (Ampere)
B. m (Meter)
C. kg (Kilogram)
D. None of these
Explanation
Wavelength is a measure of distance between two wave crests or troughs.
The SI unit for measuring distance is the meter (m), hence it is used for wavelength .
It is typically denoted by the symbol λ (lambda).
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A. Eight fifty miles per second
B. None of these
C. Two hundred miles per second
D. One lac eighty six thousand per second
Explanation
The speed of light in a vacuum is 186,282 miles per second (approximately 3 × 10⁸ m/s ). This speed is a fundamental constant in physics . It playing a crucial role in Einstein’s Theory of Relativity. Show/Hide Explanation
A. Angle
B. Refractive index
C. Mechanical equivalent of heat
D. Solid angle
Explanation
Refractive index is both unitless and dimensionless.
Refractive index is defined as the ratio of the speed of light in a vacuum to the speed of light in a medium.
Since both speeds have the same units (meters per second),
The units cancel out, making refractive index a d imensionless quantity.
It's also unitless because it doesn't have any associated units
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A. Proportionality
B. Plank’s
C. Dielectric
D. Decay
Explanation
λ (lambda) is indeed the d ecay constant.
The decay constant , λ " lambda ", the reciprocal of the mean lifetime (in s−1 ), sometimes referred to as simply decay rate The mean lifetime , τ "tau", is the average lifetime (1/e life) of a radioactive particle before decay.
These are related as follows:
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