The total magnification of a specimen viewed under a compound light microscope is determined by

Microscope lenses are those that allow an object to be magnified. These lenses are the eyepieces and the other is called objective. These lenses are called converging lenses and are on a common optical axis. The most commonly used objectives are 4, 10, 40 x and up to 100x. The eyepiece allows you to observe the image of the object selected by the lens, acting as a magnifying glass. It consists of two lenses: the lower or collector, and the upper, or eyepiece.

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.