In Physics we define a prism as any transparent solid bounded by flat faces. not parallel, which is able to separate the white light, which falls on it, into several beams colorful. The set of colored beams produced by the refraction of white light in the prism is known as the light spectrum.
We have seen that when a ray of monochromatic light falls on a prism, passing through it, this ray suffers two refractions, one on the first face (incident face) and the other refraction occurs on the second face (emergent face). Both the first and second refractions can be determined using the Snell-Descartes' Law.
Let us now imagine, or rather suppose, that a monochromatic light ray (ie, formed light ray by only one color, for example, yellow light) falls on one face of the prism at an angle i in relation to the normal line and emerge at an angle i’, also in relation to the straight line normal to the face of the prism. we call Δ (delta) the angular deviation. If we make the angle of incidence i vary, we will see that the angular deviation Δ it will also vary. Let's see the figure below.
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From the figure we can see that when the angular deviation has a very small value, the incidence angle i and the emergency angle i’ are congruent. Therefore, we have:
∆m⇒ i=i'
Being i = i’, we can say that, according to the Snell-Descartes Law, on the faces of the prism the angle of refraction r is equal to the angle of refraction ha (r = r’). Under these conditions we can mathematically write that:
A=2r and ∆m=2i-A
In summary, considering that the angular deviation is minimal, we have:
i=i'
r=r'
A=2r
∆m=2i-A
By Domitiano Marques
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
SILVA, Domitiano Correa Marques da. "Minimum angular deviation"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/desvio-angular-minimo.htm. Accessed on June 27, 2021.
