Question

If sunlight shines straight onto a peacock feather, the feather appears bright blue when viewed from 15° on either side of the incident beam of light. The blue color is due to diffraction from parallel rods of melanin in the feather. Other wavelengths in the incident light are diffracted at different angles, leaving only the blue light to be seen. The average wavelength of blue light is 470 nm. Assuming this to be the first order diffraction, what is the spacing of the melanin rods in the feather?

Answer 1

Answer:

  d = 1.82 10⁻⁶ m = 1.82 μm

Explanation:

The diffraction phenomenon is explained by a similar equation Young's double slit equation

    d sin θ = n λ

Where d is the spacing between the bars, θ is the angled diffraction, n in an integer representing the order of diffraction and λ is the wavelength of light

Let's calculate

     d = n λ / sin θ

     d = 1 470 10⁻⁹ /sin 15

     d = 1.82 10⁻⁶ m = 1.82 μm