Question

4.2 characteristics of light
red light has a wavelength of 630 nm. what is the frequency of this wave?
○ 190 hz
○ 4.8 x 10^5 hz
○ 1.9 x 10^11 hz
○ 4.8 x 10^14 hz

Explanation:

Step1: Convert wavelength to SI unit

The wavelength $\lambda = 630\ nm=630\times10^{- 9}\ m$. The speed of light $c = 3\times10^{8}\ m/s$. The formula relating the speed of light $c$, frequency $f$ and wavelength $\lambda$ is $c = f\lambda$.

Step2: Solve for frequency

We can re - arrange the formula $c = f\lambda$ to $f=\frac{c}{\lambda}$. Substitute $c = 3\times10^{8}\ m/s$ and $\lambda=630\times10^{-9}\ m$ into the formula: $f=\frac{3\times 10^{8}}{630\times10^{-9}}=\frac{3\times10^{8 + 9}}{630}=\frac{3\times10^{17}}{630}\approx4.8\times10^{14}\ Hz$.

Answer:

$4.8\times 10^{14}\ Hz$