One of the necessary conditions for total internal reflection to take place is ($i =$ angle of incidence,$i_{c} =$ critical angle).

$A$ ray of light travels from a medium of refractive index $2$ to another medium of refractive index $\sqrt{2}$. Total internal reflection takes place when the angle of incidence is

The relation between the critical angles of water and glass is:

An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of

In total internal reflection,when the angle of incidence is equal to the critical angle for the pair of media in contact,what will be the angle of refraction in degrees?

$(a)$ Figure shows a cross-section of a 'light pipe' made of a glass fibre of refractive index $1.68$. The outer covering of the pipe is made of a material of refractive index $1.44$. What is the range of the angles of the incident rays with the axis of the pipe for which total internal reflections inside the pipe take place,as shown in the figure.
$(b)$ What is the answer if there is no outer covering of the pipe?