What is an example of total internal reflection at work? the intensity of light coming out of a thin plastic thread is same as that of light entering it. a ray of light entering a glass cube gets refracted. a ray of light in air hits a shiny surface and bounces off. a ray of light entering a ruby gets refracted. physics

The intensity of light coming out of a thin plastic thread is same as that of light entering it.

Explanation:

As we know that in total internal reflection when light traveling in a denser medium and it then move out of that medium to a rarer medium then in that case the light has tendency to bend into the same medium again.

This phenomenon is known as total internal reflection

so here as per the formula of Snell's law we can say

now we know that

so at limiting condition we know the angle of refraction is 90 degree

so we will have

so here correct answer will be

The intensity of light coming out of a thin plastic thread is same as that of light entering it.

as all other statements light is not moving from rare to denser medium in which total internal reflection is not possible

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.