Total Internal Reflection and Critical Angle
When light travels from a medium with a higher refractive index to one with a lower refractive index, Snell's law seems to require in some cases (whenever the angle of incidence is large enough) that the sine of the angle of refraction be greater than one. This of course is impossible, and the light in such cases is completely reflected by the boundary, a phenomenon known as total internal reflection. The largest possible angle of incidence which still results in a refracted ray is called the critical angle; in this case the refracted ray travels along the boundary between the two media.
For example, consider a ray of light moving from water to air with an angle of incidence of 50°. The refractive indices of water and air are approximately 1.333 and 1, respectively, so Snell's law gives us the relation
which is impossible to satisfy. The critical angle θcrit is the value of θ1 for which θ2 equals 90°:
Read more about this topic: Snell's Law
Famous quotes containing the words total, internal, reflection, critical and/or angle:
“You have got to prepare for a lifetime of the pillory, for whatever you do will be seen as wrong by total strangers, up until and including the time when whatever your child does will be seen as wrong by total strangers.”
—Sonia Taitz (20th century)
“If the Revolution has the right to destroy bridges and art monuments whenever necessary, it will stop still less from laying its hand on any tendency in art which, no matter how great its achievement in form, threatens to disintegrate the revolutionary environment or to arouse the internal forces of the Revolution, that is, the proletariat, the peasantry and the intelligentsia, to a hostile opposition to one another. Our standard is, clearly, political, imperative and intolerant.”
—Leon Trotsky (1879–1940)
“The reflection of her here, and then there,
Is another shadow, another evasion,
Another denial. If she is everywhere,
She is nowhere, to him.
But this she has made.”
—Wallace Stevens (1879–1955)
“A third variety of drama ... begins as tragedy with scraps of fun in it ... and ends in comedy without mirth in it, the place of mirth being taken by a more or less bitter and critical irony.”
—George Bernard Shaw (1856–1950)
“Modesty is the only sure bait when you angle for praise.”
—Philip Dormer Stanhope, 4th Earl Chesterfield (1694–1773)