The speeds of the light wave will be 0.56×10⁻⁵ m/sec.It is the ratio of the speed of the wave and the refractive index.
The distance between two successive troughs or crests is known as the wavelength. The peak of the wave is the highest point, while the trough is the lowest.
Given data;
the wavelength,λ= 640 nm
Wave's speed,v=?
Refractive index,n
The refractive index is the ratio of the square root of the dielectric constant;
[tex]\rn n= \sqrt{78}\\\\ n= 8.8[/tex]
The relationship between the wave's wavelength, refractive index, and speed of light wave is given as;
[tex]\rm \lambda = \frac{c}{n} \\\\ c =n \times \lambda \\\\\ c= 8.8 \times 640 \times 10^{-9} \\\\ c= 0.56 \times 10^{-5} \ m/sec[/tex]
Hence, the speed of the light wave will be 0.56×10⁻⁵ m/sec.
To learn more about the wavelength refer to the link;
https://brainly.com/question/13533093
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