Student John Paul Anto's Microwave Oven Experiment - Experimental verification of speed of Electromagnetic waves

 12P08 Electromagnetic Waves

Student John Paul Anto's Microwave Oven Experiment - Experimental verification of speed of Electromagnetic waves

 

If you have access to a microwave oven, see if you can do this simple 10 minutes experiment in your microwave.

1. Remove the turn table inside the oven

2. Place an uncooked Chappathi (Tortila) or similar flour item spread out

3. Switch on the oven for a nominal time ( may be 1 minute or 2 minutes as required)

4. Open the oven and look for any black spots where the heat is concentrated

5. Measure the distance between the black spots using a measuring scale (few cm expected)

6. In the instrument label in the back side of oven look for any frequency of microwaves used.

7. We are looking for the Speed of Microwave c = Frequency x Lambda, calculations from the above values obtained.

8. Any videos or pictures of the experiment will be very helpful for educational purpose may be to upload in youtube.

 

Microwave is an Electromagnetic wave. All EM waves such as light, radio wave, microwave, infrared wave, uv rays, x rays, gamma rays travel at the speed of light c = 3 x 10⁸ m/s. This experiment is an attempt to experimentally verify the speed of microwaves.

 

 

Before Heating

After Heating, approx.6 cm gap between black spots

Label behind the microwave

Standing waves or stationary waves

Black Spots in the chappathi represent the hot spots which is caused by the highly vibrating points on the standing waves called Anti Nodes with maximum displacements (zero displacement points are Nodes).

Distance between black spots ~6 cm, so wavelength = 12 cm,

Frequency = 2450 MHz

Speed of microwaves,

 c = Frequency x Wavelength 

=  2450 x 10⁶ (1/s) x 12 x 10^-2 (m) 

= 2.94 x 10⁸ m/s which is very close to 3 x 10⁸ m/s

Speed of microwaves happens to be equal to the speed of light. Light is also an Electromagnetic wave.

Principle of Working of Microwave Oven: The water molecule's one of the resonant frequency is around 2.4 GHz. When the microwave is emitting waves at this frequency 2450 MHz = 2.45 GHz, the water molecules in the food is made to vibrate at these high frequencies (microscopic), which we call it as high temperature (macroscopic), which is made use to cook the food.