Armand Hippolyte Louis Fizeau:
Hippolyte Fizeau measures the speed of light in the year 1849, in his Fizeau Experiment.
This post is just for an illustration of the modern Fizeau Experiment just for a basic understanding.
A modern Fizeau Experiment Setup (for basic Understanding):
Toothed Wheel: Moterize the rotating toothed wheel. (Width of the teeth of the wheel is equal to the width of the gap between the teeth of the wheel).
Semi-reflective mirror: A partially glazed glass that allows some light to pass through it and some light to get reflected. (It is set in the tilted position)
Reflecting Mirror: It reflects back the light beam when the light beam incident on it.
Light Source: A laser work as a light source in this setup.
Observer: Observer is used to observing the coming light beam.
Working Principle:
After switching on a light source, the light passed through the semi-reflective mirror, and after that light passes through the outer rim of the toothed wheel, after light hit the reflecting mirror and reflected back and again passes through the outer rim of the toothed wheel and then the incidence on the semi-reflective mirror and after that light beam reflected and observe through the observer.
Based on the number of teeth in the toothed wheel, and the speed of the rotation of the toothed wheel, and knowing the distances between the mirror and toothed wheel, he became able to calculate the speed of light.
The first terrestrial measurement of the speed of light is measured in the year 1849, by Hippolyte Fizeau in his Fizeau Experiment.
Reference Source:
[1] ayuta. How to find the speed of light (Fizeau experiment). YouTube. Published online March 8, 2020. Accessed April 4, 2022. https://www.youtube.com/watch?v=a6gl8KZM0PM
[2] Dr Radhakrishnan M.V. FIZEAU’S EXPERIMENT / DETERMINATION OF SPEED OF LIGHT. YouTube. Published online October 1, 2021. Accessed April 4, 2022. https://www.youtube.com/watch?v=bD06G8Ha5fs
[3] Schuster D. Fizeau’s 1850 Experimental Measurement of the Speed of Light | Doc Physics. YouTube. Published online February 12, 2013. Accessed April 4, 2022. https://www.youtube.com/watch?v=h_UMabvPrws
[4] Adkins J, Orzel J, Vandemark K. Speed of Light Measurement (Foucault Method). https://sciences.csuohio.edu/sites/csuohio.edu.sciences/files/media/physics/documents/Speed%20of%20Light_0.pdf
[5] Chegg.com. Chegg.com. Published 2022. Accessed April 4, 2022. https://www.chegg.com/homework-help/definitions/the-fizeau-wheel-2
[6] The speed of light controversy – Pyroistech. Pyroistech. Published May 21, 2021. Accessed April 4, 2022. https://www.pyroistech.com/the-speed-of-light-controversy/
[7] uclaphysicsvideo. How to Measure the Speed of Light. YouTube. Published online January 29, 2013. Accessed April 4, 2022. https://www.youtube.com/watch?v=H9kZTm4Xm-8