Which of the following is a dimensionless quantity?
Correct answer: C. Refractive Index
- A. Power
- B. Frequency
- C. Refractive Index
- D. Impulse
Explanation
Refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light in that particular medium. Since the speed of light in vacuum and the speed of light in different mediums have the same dimensions, a quantity which is the ratio of these two will be dimensionless. Therefore, option C is the correct answer.For power, the formula is Energy/time and its dimensions are ML2T-3 .For frequency, the formula is 1/time period and its dimension is T-1.For impulse, the formula is force x time and its dimensions are MLT-1 . So amongst all four, only refractive index is the one having no dimensions.
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