A beam of light enters a block of flint glass (n = 1.65) at a 24 degree degree a

Question

A beam of light enters a block of flint glass (n = 1.65) at a 24 degree degree angle from the normal, as illustrated. Calculate the path the light takes until it leaves the glass. Don't worry about the exact position, but assume the illustration is reasonably accurate. Calculate the exact angles the light travels at each time it refracts or reflects (you have to figure out which it does), and remember that the normal for the side of the glass block is perpendicular to the normal for the top of the glass block. Finally, assume all the corners of the glass block are right angles.

Explanation / Answer

This is refraction and this follows Snell's law:

n1 Sin(x1)=n2 Sin(x2) , 1,2 are mediums.

1*Sin(24°) = 1.65 Sin(x2)

0.41/1.65 = Sin(x2)

0.248= Sin(x2)

Sin-1(0.248) = x2;

So, x2=14.36°from the normal (in the flint glass)

When light refracts into a denser medium, it always bends towards the normal.

Again,t his refracted wave will be reflected from the inner surface of top of rectangular slab of flint glass, and angle made by incident ray(actualy refracted) from the normal to top surface will be 90-14.36= 75.64°.

And this follows laws of reflection, so, ray reflected from top Surface will be reflected at 75.64° too.

Some part of the incdent ray may get refracted into the air medium from top surface, and this will be solved again by Snell's law:

1.65*Sin(75.64) = 1.Sin(x'2)

1.65*0. 969= Sin(x2)

X2=160° in air medium. This means ray is Totally internally Reflected into the glass only and nothing got refracted from top surface.

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