Concrete is the most common artificial composite material of all and typically consists of loose stones (aggregate) held with a matrix of cement. Concrete is a very robust material, much more robust than cement, and will not compress or shatter even under quite a large compressive force.
2) Y-axis contains absolute brightness Why do astronomers use the H-R Diagram? Astronomers use H-R Diagrams to classify stars and to understand how stars change over time.
Also in astigmatism corrections, after the amount, you will see an (X), this stands for axis. Astigmatism has a maximum power in a certain meridian or direction, which we call axis. Axis run from 1 to 180 and then starts all over again. Axis 0 is the same as axis 180 and we never write axis 0, itâs always 180.