Physics of why wings of Morpho butterflies exhibit different color pattern when viewed from different angles?
Though these butterflies mostly prefer to remain hidden to protect themselves but when their wings open they display beautiful blue colour which changes with the angle of viewing. The colours are primarily due to two types of light-reflecting wing scales namely ground scales and
glass scales. Ground scales absorb longer wavelengths
of light, and reflect lower wavelengths hence, light reflected from the wing is blue to purple in
color. Some species of morphos have a layer of transparent glass scales
covering the ground scales. This layer of glass scales acts as a diffraction
grating, increasing the angle over which light
reflected from the ground scales is spread. According to the principle of interference of light, there is constructive and destructive interference which gives colour pattern in white light similar to the colouring of thin films. As the path length and phase angle is different for the different angle the wavelengths corresponding to maxima and minima also change that leads to displaying a different pattern.
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