light travels from ethanol intro crown glass. what's the brewster angle in this situation? illustrate your answer with a light ray diagram. what's the signifcance of this angle of incidence?
n1=1.36for ethanol
nR=1.52 for crown glass
tanangleB=nR/ni
=1.52/1.36
=1.12 (48.2 degrees)
the only thing that I have in the diagram is the face that both the incident and reflected rays are 48.2 degrees in the ethanol..not even sure if that is right.
not sure how to draw it or what the signicance is....please explain.
physics - bobpursley, Saturday, January 16, 2010 at 3:44pm
Bob - I looked at the website you gave me. In order to draw it, do I need to also figure out the angle of incidence and reflection? If so, how do i do that...thanks
physics - bobpursley, Saturday, January 16, 2010 at 5:25pm
WEll, you have the angles of incidence of 48.2, so use snell's law to get the angle of refracation.
okay so I did that, and have my diagram drawn now, but what is the significance? I know that the angle of incicdence, from Brewster'slaw, is 48.2 degrees, and the angle of refraction, from Snell' Law, is 41.84. However this wouldn't be total internal reflection, since its going from ethanol -->crown glass, which is lower index of refraction to higher and total internal reflection requires from higher to lower. So why is significant about this then?
The Brewster angle and the Total Internal Reflection angles are different. When light is incident at the Brewster angle, the refracted wave and reflected waves are perpendicular.
http://en.wikipedia.org/wiki/Brewster's_angle
The Brewster angle is the angle of incidence at which the reflected light becomes polarized. To calculate the Brewster angle, you need to use the equation tan(angleB) = nR/ni, where nR is the refractive index of the medium the light is entering (in this case, crown glass) and ni is the refractive index of the medium the light is coming from (in this case, ethanol).
In the given situation, nR = 1.52 and ni = 1.36. Plugging these values into the equation, we have:
tan(angleB) = 1.52/1.36
angleB = arctan(1.12)
angleB ≈ 48.2 degrees
To draw the light ray diagram, first draw a line representing the boundary between ethanol and crown glass. The angle of incidence (48.2 degrees) should be measured from the normal (perpendicular to the boundary). The incident ray should be drawn at this angle, and the reflected ray should be drawn at the same angle but on the opposite side of the normal.
The significance of the Brewster angle is that at this particular angle of incidence, the reflected light becomes completely polarized, meaning that it oscillates in a single plane. This is because when light strikes a surface at the Brewster angle, the reflected and refracted rays are perpendicular to each other.
In this specific situation, the significance is that when light passes from ethanol into crown glass at the Brewster angle, the reflected light will be completely polarized. This can be useful in applications where it is desirable to have polarized light, such as in polarizing filters or certain types of imaging techniques.