A light ray of wavelength 589nm in vacuum passes through water. What is the wavelength of this light in water?

1 answer

To find the wavelength of light in a medium like water, you can use the formula that relates the wavelengths in different media to the indices of refraction:

\[ \lambda_{medium} = \frac{\lambda_{vacuum}}{n} \]

Where:

  • \(\lambda_{medium}\) is the wavelength in the medium (water in this case),
  • \(\lambda_{vacuum}\) is the wavelength in vacuum (589 nm for this light ray),
  • \(n\) is the index of refraction of the medium (for water, \(n \approx 1.33\)).

Now, plug in the values:

\[ \lambda_{water} = \frac{589 , \text{nm}}{1.33} \]

Calculating this gives:

\[ \lambda_{water} \approx \frac{589 , \text{nm}}{1.33} \approx 442.11 , \text{nm} \]

So, the wavelength of the light in water is approximately 442 nm.