How can you use a microwave to find the speed of light?

Answer 1

One way, is to turn on your light switch and observe how long it takes for the light to reach to the other side of the room. (How long it takes for the room to go from dark to light.) Be careful not to blink or you'll miss it.

Answer 2

-- Put a smooth slab of chocolate or ice flat in the microwave oven.

-- Zap it for 10 or 15 seconds at a time and check it, until you begin to see

spots where it's starting to melt.

-- The spots will be arranged in columns and rows. Measure the distance

between spots in one column or in one row. The distance will be roughly

6.1 centimeters. Write it down.

-- Look on the information plate inside the oven or on the back. It will tell the

frequency of the energy it uses to cook. The frequency will be 2.45 GHz.

-- The speed of the wave is (wavelength in meters) x (frequency in hertz).

-- The distance between the spots is 1/2 wavelength.

The wavelength is 12.2 centimeters = 0.122 meter.

-- 2.45 GHz is 2,450,000,000 Hz

-- The wave speed is (0.122) x (2,450,000,000) = 298,900,000 meters per second.

That number, which you calculated using only a ruler and some ice,

is only about 0.27% lower than the actual speed of light in air.

Oh ! Did I forget to mention that the speed of microwaves is the same as

the speed of light ? Sorry.