How to determine the speed of light

How to determine the speed of light

On representations of modern physics, the speed of light in a vacuum is a fundamental constant, and its value is equal 299,792,458 ± 1.2 m/s. In 1676 its approximate value was found for the first time by Olaf Remer, studying eclipses of satellites of Jupiter. Modern laboratory methods of determination of the speed of light are based on effect of an aberration and allow to calculate it with very high precision. In house conditions to confirm researches of scientists it is possible by means of the ordinary microwave.

It is required to you

  • - Microwave oven;
  • - ruler;
  • - egg.


1. Light is an electromagnetic wave therefore mean the speed of distribution of electromagnetic waves by the speed of light. The ordinary microwave oven in your kitchen generates electromagnetic waves and heats food because these waves influence molecules of water and fats in food and force them to fluctuate strongly that lifts food temperature. The speed of light and speed of waves in your microwave differ in nothing. For determination of speed of an electromagnetic wave it is necessary to use a formula: with = yv where y is wavelength, and v is its frequency.

2. It is possible to look at the frequency of the waves radiated by the microwave in the specification to the device, besides, it usually is specified on a back cover. Turn your microwave and find the plate with specifications. Frequency of radiation will be specified in MHz, it is equal in standard modern microwaves 2450 MHz. Having learned wave frequency, transfer it to hertz: 2450 MHz = 2,450,000 Hz.

3. Now determine wavelength. In your microwave there is a special rotating support, it is made in order that food was warmed evenly. The fact is that waves in the furnace interfere and create hot and cold zones. If the rotating support was not, a part of food would get to a hot zone, and a part in cold. Having removed a support, you will be able to calculate hot zones. Wavelength will be equal to distance between hot zones increased by two.

4. Take egg, separate protein from a yolk. Place protein on a flat plate, pull out the turning support from the microwave and place in the device a plate with protein. Turn on the furnace and wait 20 seconds. You will see that protein was baked unevenly, and taking into account impact on it of hot and cold zones.

5. Measure distance between hot zones a ruler and increase it by two. Transfer the received value of wavelength to meters. Let the distance between hot sites be equal to 61 mm, then wavelength will be equal 122 mm, or 0.122 m.

6. Substitute the received values of frequency and wavelength in a speed formula: with = 0.122 m * 2,450,000 Hz = 298,900,000 m/s. You received value of the speed of light very close to officially measured by scientists, and the error is connected with inaccuracy of measurement of wavelength.

Author: «MirrorInfo» Dream Team