Critical angle is the angle of incidence in the optically denser medium for which the angle of refraction in the less dense medium is 90degree. Total internal refraction occurs when the angle of incidence is greater than the critical angle.

Transverse waves are waves that travel in a direction PERPENDICULAR to the direction of the vibrations. Whereas longitudinal waves are waves that travel in a direction PARALLEL to the direction of vibration.

Theres hell lot of things that is needed to go into my brain,
but it seems like my brain is not functioning.
I swear i hate Os.