Asked in PMC Practice Test 12 (2021) 2021Moderate

Michelson measured the length of standard metre in terms of the wavelength of:

Correct answer: C. Red cadmium light

  • A. Green cadmium light
  • B. Violet cadmium light
  • C. Red cadmium light
  • D. Blue cadmium light

Explanation

Michelson measured the length of the standard meter using the interference fringes produced by red cadmium light. He used a device called an interferometer to measure the wavelength of the light and used it to determine the length of the standard meter.The interferometer creates interference patterns by splitting a beam of light into two paths, allowing them to recombine and create an interference pattern. By measuring the fringe pattern and knowing the wavelength of the light source, the length of the standard meter can be determined.

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Physical quantities combine a numerical value with a unit, and are expressed using SI base units or derived units such as newtons, joules and pascals. The topic covers prefixes, unit conversion, dimensional analysis, significant figures and measurement uncertainty, while distinguishing scalar quantities from vectors where direction matters.

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