Ascaffold of mass 40 kg and length 4.5 m is supported in a horizontal position by

Explanation:

Given:

Here we consider the mass of the beam as uniformly distributed load concentrated at mid-span.

Using the schematic diagram:

Balancing forces:

..............................(1)

Balancing moment about point A:

......................................(2)

Putting value from eq. (2) into eq. (1)

the index of refraction of the second medium is lower

Explanation:

take an exaple of a light ray from air to water that is optically denser the ray is refracted to the normal thus lowering its index of refraction