Test: Total Internal Reflection & Refraction at Spherical Surfaces (February 24) - NEET MCQ

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

The Critical Angle
a light ray is in the more dense medium and approaching the less dense medium.
The angle of incidence for the light ray is greater than the so-called critical angle.
When the angle of incidence in water reaches a certain critical value, the refracted ray lies along the boundary, having an angle of refraction of 90-degrees. This angle of incidence is known as the critical angle; it is the largest angle of incidence for which refraction can still occur. For any angle of incidence greater than the critical angle, light will undergo total internal reflection.

Light remains confined within the core of simple optical fibre because of Total internal reflection from core cladding boundary.
Light is confined within the core of a simple optical fiber by. If light hits a boundary of a material of lower refractive index at a steep enough angle, it cannot get out and it's reflected back into the high index medium, as in the figure below.
An optical fibre is a thin rod of high-quality glass. Very little light is absorbed by the glass.Optical fibres can carry more information than an ordinary cable of the same thickness. The signals in optical fibres do not weaken as much over long distances as the signals in ordinary cables.
Total internal reflection. When light traveling in an optically dense medium hits a boundary at a steep angle (larger than the critical angle for the boundary), the light is completely reflected. This effect is used in optical fibers to confine light in the core.
The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances.
 

Mirage is formed by total internal reflection in deserts where due to heating of earth, refraction index of air near the surface of earth becomes lesser than above it.

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.
 

Here, R₁ = 20cm,R₂ = −40cm, f = 20cm
Using lens makers formula we get,


⇒ μ = 5/3

When refractive index of lens is equal to the refractive index of liquid, the lens be have lik e a plane surface with focal length infinity.

Area of square card = 1 mm × 1 mm = 1 mm²
Focal length of magnifying lens, f = +10 cm
Object distance, u = -9 cm
According to thin lens formula

or v = -90 cm

∴ Apparent area of the card through the  lens 
= 10 × 10 × 1 mm²
 = 100 mm²
 = 1 cm²

When the curved surface of the lens faces the object, the spherical aberration is smaller. The total deviation is shared between the curved and the plane surfaces.

Here, u = -45 cm,  v = 90 cm 

when the needle is move 5 cm away from the lens,
u = -(45 + 5) = -50 cm

∴ Displacement of image = v - v' = 90 - 75 = 15 cm, towards the lens