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MCAT Physics Question — Refraction

The full spectrum of visible light created when light passes through a prism results from which of the following phenomenon?

A) Refraction

B) Reflection

C) Dispersion

D) Diffraction




This question is testing your understanding of optics and the physical phenomenon that results when white light shines through a prism of glass resulting in a rainbow of colors.

It is important to note that when light changes mediums, the frequency of the light does not change. Therefore, all the colors that comprise white light maintain their frequency but have a change in wavelength with a corresponding change in velocity. Since each color has a slightly different wavelength, each color refracts slightly differently. Ultimately, violet light has the largest decrease in wavelength and thus the highest index of refraction. Oppositely, red light has the smallest decrease in wavelength and the lowest index of refraction.

The splitting of white light into its components of varying wavelengths is best described by dispersion. Thus C is the correct answer.

Refraction is a component of dispersion but it only explains the way light bends and not the way white light is separated into the full color spectrum.

Reflection occurs when light travels from a medium with a higher refractive index to one with a lower refractive index in which none of the light refracts, but instead reflects staying in the same medium as initially.

Diffraction is the process of light spreading out after it passes through a narrow opening.


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