why is 1 4 5 a cadence

[peter_traj]

gday all. im from sydney austalia and my name is peter.before i ask a question i would like to say that the theory articles posted on this site are fantasic and are EXTREMELY helpful.i have been playing the guitar for only 6 months any i really want to learn the theory side of things. any way here is my question. i will have many more but ill just start with one for now.
when you talk of a cadence in music i am assuming that you mean that the chords or notes sound good when played after each other.but why is the 1 4 5 such a strong cadence? has it something to do with the intervals being so many steps apart or is there some other reason. any reply would be greatly appreciated. thanks.

[szulc]

What is a cadence ?
A cadence is the point at which a piece of music is brought to a close. It is a resolution of discord, a point of stability, rest and consonance.

Authentic cadences
V-I or V-i
In the major and minor tonalities this is the strongest type of cadence and powerfully determines the key center. How strongly the final is felt to be at rest, depends on whether or not the authentic cadence is perfect or imperfect.

The perfect cadence is always authentic - it uses a V - I or V - i progression, but both triads are in root position, and the tonic note of the scale is in the highest part.

The imperfect cadence is also always authentic, but now the triads are not in root position, and/or the tonic is not in the highest part.

Plagal cadence
IV-I

Deceptive
V-vi or V-IV


see this link
http://www.andymilne.dial.pipex.com/Cadentialprog.shtml#Three triad cadences