Question

Combing your hair leads to excess electrons on the comb. How fast would you have to move the comb up and down to produce red light?

Short answer

The frequency to move the comb up and down to produce red light is \(5 \times {10^{14}}\;Hz\).

Step-by-step solution

Definition of frequency

Frequency is the number of waves that pass through a specific spot in a specific length of time.

Given information and Formula to be used

The wavelength of red light: \({\lambda _{red{\rm{ }}}} = 600\;nm = 0.6 \times {10^{ - 6}}\;m\)

The speed of light value is: \(c = 3 \times {10^8}\;m/s\)

For an electromagnetic wave, the relationship between propagation speed, wavelength, and frequency is given by,

\(c = f\lambda \)

Calculate the frequency

Consider the given formula and simplify,

We have

\(\begin{aligned} c &= f\lambda \\3 \times {10^8} &= f \times 0.6 \times {10^{ - 6}}\\f &= 5 \times {10^{14}}\;Hz\end{aligned}\)

Therefore, frequency is \(5 \times {10^{14}}\;Hz\).