Write the scientific concept for the following definitions: 1- The quantities those can be expressed in terms of the basic quantities. 2- A technique used to check the validity of an equation or to assist in deriving an equation. 3- The distance traveled by light in a vacuum during a given time. 4- The mass of a specific platinum-iridium cylinder kept at the International Bureau of weights and measures, France. 5- The time required to radiate a known number of oscillations from a cesium atom 133. 6- It denotes the physical nature of a quantity. Solve the following problems: 1- Using the dimensional analysis, test the validity of the equation: T=2gL where T is periodic time, is constant, L is length and g is acceleration due to gravity