Question

Hello, what does the first condition mean?

Answer 1

Answer:

An object at rest is described by Newton's First Law of Motion. An object in static equilibrium has zero net force acting upon it. The First Condition of Equilibrium is that the vector sum of all the forces acting on a body vanishes.

Explanation:

Answer 2

Answer:

see below

Explanation:

the first condition means that the light ray inside the optically denser medium hits the surface of the optically less dense medium.

this in simple words means, light must be travelling from am optically denser medium to an optically less dense medium

hope this helps :)