# Chemistry of Food and Cooking

## CONTENTS OF CURRICULUM UNIT 20.02.04

- Curriculum Unit
- Waves Background
- Electromagnetic Waves Background
- Energy of an Electromagnetic Wave
- How can infrared radiation and microwaves be used to heat food?
- History of the Microwave Oven
- A Microwave Oven
- Water
- Why Does a Microwave Oven Work?
- Molecular Motion
- Interaction of Electromagnetic Waves with Matter
- Activities and Laboratory Experiments
- Bibliography
- Appendix on Implementing District Standards
- Endnotes

### Unit Guide

## How Do We Use Electromagnetic Waves to Cook Food?

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## Energy of an Electromagnetic Wave

As one moves along the electromagnetic (EM) spectrum from longer wavelengths, such as radio waves, to shorter ones, such as gamma rays, both frequency and energy increase. But why is this? All EM waves travel at the speed of light, which is about 3 x 10^{8} m/s in vacuum. To calculate the speed of a wave, Equation 1 is used.

c** = ***νλ *Equation 1,

where *c* is the speed of light in the unit of m/s, *ν* is frequency in hertz, and *λ *is the wavelength in meters. The unit hertz (Hz) is equal to the number of complete waves passing a given point per second. For any wavelength on the EM spectrum, the wavelength multiplied by its frequency is equal to the speed of light. Light or any other EM wave can be considered as photons which carry a discrete amount of energy. It is possible to calculate the energy of a photon based on the EM waves’ frequency and Planck's constant using the following equation.

*E* = h*ν *Equation 2,

where *E* is equal to energy, h is Planck’s constant, and *ν* is frequency. Planck’s constant is 6.626 x 10^{-34} J▪s. Energy in Joules is equal to Planck's constant in the unit of J▪s times the frequency in Hz (Equation 2). With this equation, it is possible to observe that as frequency increases, so does the energy. Because Planck’s constant is a very small number, the amount of energy carried by a single photon is also very small.