Which of the following is dimensionless quantity?
Correct answer: C. Refractive Index
- A. Power
- B. Frequency
- C. Refractive Index
- D. Impulse
Explanation
Option A: Power is the rate at which energy is transferred. It is measured in watts, which are equivalent to joules per second. Option B: Frequency is the number of oscillations per unit time. It is measured in hertz, which are equivalent to cycles per second. Option C: The refractive index is a dimensionless quantity.A dimensionless quantity is a quantity that has no units. It is a pure number that is independent of any physical dimensions.The refractive index is a measure of how much a light beam bends when it passes from one medium to another. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium.The refractive index has no units because it is a ratio of two quantities with the same units. The speed of light in a vacuum is a physical quantity with units of meters per second. The speed of light in a medium is also a physical quantity with units of meters per second. Option D: Impulse is the product of force and time. It is measured in newton-seconds.
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Physical quantities are expressed with SI base and derived units, while measurement limits are described through accuracy, precision, absolute and percentage error, and significant figures. Dimensional analysis checks equations, derives relationships and detects inconsistent units, but it cannot determine numerical constants or distinguish quantities with identical dimensions.
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