# How to Calculate Hertz to Joules

Written by oxana fox
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The metric (International) system defines a hertz (Hz) as a unit of frequency, while a joule (J) represents a unit of energy. The conversion between these units is based on the Planck's equation written as: Energy = Planck Constant x Frequency. It allows you to calculate an energy of the electromagnetic radiation, such as light, if you know the frequency. Use a convenient online energy converter or a calculator to convert hertz to joules.

Skill level:
Easy

### Things you need

• Computer with Internet access
• Calculator

## Using Online Converter

1. 1

Open the Energy Converter in any web browser using the link in Resources.

2. 2

Set the unit "Hz" (hertz) in the column "Frequency."

3. 3

Enter the frequency value: "20000," for example, in the box under "Hz."

4. 4

Set the unit "J" (joule) in the column "Energy." Then read the energy in joules in the box under "J." In the example, 20000 Hz converts to 1.3252 x 10^-29 J.

## Using a Calculator

1. 1

Retrieve the Planck constant value using the link in Resources: 4.13566733 x10^-15 eV s. Note that the Planck constant is usually given in electron volts (eV), which is another unit for energy.

2. 2

Multiply the frequency and the Planck constant to calculate the energy in eV. For example, if the frequency is 50,000 Hz, then the photon energy is 50,000 Hz x 4.13566733 x 10^-15 eV s = 2.07 x 10^ -10 eV.

3. 3

Multiply the energy in eV by 1.6021765 x 10^-19 to convert it to joules (J). In this example, the energy of 2.07 x 10^ -10 eV corresponds to (2.07 x 10^ -10 eV) x (1.6021765 x 10^-19) = 3.31 x 10^ -29 J.

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