Carbon disulfide (n = 1.63) is poured into a container made of crown glass (n = 1.52). What is the critical angle for internal reflection of a ray in the liquid when it is incident on the liquid-to-glass surface?
Refractive index of glass with respect to liquid:
n = 1.52/1.63 = 0.9325
thus, critical angle, i = sin-1(n) = 68.8 degrees
What is the relation between critical angle and refractive index?
Critical angle is
Which of the following phenomena takes place inside an optical fiber ?
Light is confined within the core of a simple optical fiber by:
The critical angle for the material of a prism is 45° and its refracting angle is 30°. A monochromatic ray goes out perpendicular to the surface of emergence from the prism. What is the angle of incidence on the prism?
Using the equation for the critical angle
45o= arcsin(1/n1) à n1=1/sin45o= √2
From the figure,
sin β/sin γ à sin β=n1sin γ/n2 à
β=arcsin(n1.sin γ/n2)=arcsin(√2sin30o/1)=arcsin(√2/2)à β=45o
Total internal reflection occurs when
Mirage is caused due to
We have a right angled isosceles prism, Its refractive index is 1.5. If we incident a ray normally on one of the two perpendicular surfaces, which of the following phenomenon will take place?
Critical angle will be, sin−1(1/1.5) = 41.8. The angle of incidence inside the prism will be 45. Since it is more than critical angle, the light ray will be internally reflected.
Total internal reflecting mirrors are preferred over plane mirrors because
Whenever there is reflection on any surface there is refraction also beneath the surface.
The energy of the incident beam is partially reflected and partially absorbed.
Even a good mirror reflects nearly 80%of the incident light only.
At normal incidence (Incident perpendicular to the surface) there is no reflection and all the light rays pass through the surface.
When a ray passes through a denser medium and tries to enter a rarer medium and if the angle of incidence is more than the critical angle, we say there is total internal reflection.
The total here implies that there is no refraction at all. The entire ray is refracted.
Therefore when we use totally reflecting prisms, there is no energy lost due to normal incidence from air to glass and there is TOTAL (no partial refraction) reflection inside the prism.
Thus the light is reflected almost 100% in totally reflecting prisms and hence they are preferred even though it costs high.