# The second is defined as the time it takes

The second is defined as the time it takes for 9,192,631,770 wavelengths of a certain transition of the cesium-133 atom to pass a fixed point. What is the frequency of this electromagnetic radiation? What is the wavelength?

#### Solution:

The frequency of this electromagnetic radiation is already given to us in the question. It is simply 9,192,631,770 per second.

To calculate the wavelength, we will use this formula:

$\lambda=\dfrac{c}{v}$

(Where $\lambda$ is the wavelength, $c$ is the speed of light, and $v$ is frequency)

Speed of light = $2.99792458\times 10^8\dfrac{m}{s}$

Substituting the values we know and solving for $\lambda$ gives us:

$\lambda=\dfrac{2.99792458\times 10^8\dfrac{m}{s}}{9,192,631,770/s}$

$\lambda=0.0326122557$ m