A pane of glass, n_glass = 1.5, is in air. Light of a certain intensity strikes

Question

A pane of glass, n_glass = 1.5, is in air. Light of a certain intensity strikes the pane at normal incidence; some of the light is reflected from the front surface, some of the light goes through the glass itself and is reflected from the back surface. Assume no secondary reflections. What percentage of the original light is reflected from the front surface? What percentage of the original light is reflected from the back surface? What percentage of the original light is transmitted all the way through the pane? Light is incident on a pane of Plexiglas (index of refraction 1.51) at an angle of 35degree to the normal. What is the angle that the reflected light makes with the normal? What is the angle that the refracted light makes with the normal? What is the velocity of the light in the Plexiglas? What is the critical angle for this system, and which way does the light have to be going? That is, does the light go from the Plexiglas to the vacuum or from the vacuum to the Plexiglas? A convex lens has a focal length of magnitude |f| = 6cm. An object is placed 2.5cm from the lens. The dark lines on the grid below each represent 1cm. Make sure your rays are dark enough to see. A pane of glass, n_glass = 1.5, is in air. Light of a certain intensity strikes the pane at normal incidence; some of the light is reflected from the front surface, some of the light goes through the glass itself and is reflected from the back surface. Assume no secondary reflections. What percentage of the original light is reflected from the front surface? What percentage of the original light is reflected from the back surface? What percentage of the original light is transmitted all the way through the pane? Light is incident on a pane of Plexiglas (index of refraction 1.51) at an angle of 35 degree to the normal. What is the angle that the reflected light makes with the normal? What is the angle that the refracted light makes with the normal? What is the velocity of the light in the Plexiglas? What is the critical angle for this system, and which way does the light have to be going? That is, does the light go from the Plexiglas to the vacuum or from the vacuum to the Plexiglas? A convex lens has a focal length of magnitude |f| = 6cm. An object is placed 2.5cm from the lens. The dark lines on the grid below each represent 1cm. Make sure your rays are dark enough to see.

Explanation / Answer

14.2

a)

according to law of reflection

angle of incidence = angle of reflection = 35

b)

i = angle of incidence = 35

r = angle of refraction

n1 = index of refraction of air = 1

n2 = index of refraction of plexiglas = 1.51

using snell's law

n1 Sini = n2 Sinr

1 Sin35 = 1.51 Sinr

r = 22.3

c)

c = speed of light in vaccum = 3 x 108 m/s

V = c/n2 = (3 x 108 ) / 1.51 = 1.986 x 108 m/s

d)

C = critical angle = Sin-1(1/n2) = Sin-1(1/1.51) = 41.3

the light has to travel from denser to rarer medium . hence plexiglas to vaccum

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