That is, if you observe the spectrum of a star and can determine the wavelength where the emission peaks (Î»max), you can calculate that starâs temperature. Here is another copy of the plot that we studied in Lesson 3: Figure 4.1: Two-dimensional plot of the spectrum of a blackbody with different temperatures.
Igneous rocks usually contain the most crystals. The longer it takes the magma to cool, the larger the crystals.
1 Aphanitic igneous rocks have a fine-grained texture and most of their crystals are too small to see with the naked eye. 2  You will need to use a magnifying glass to observe the crystals in aphanitic rocks. 3  Igneous rocks that form too quickly for crystals to form have what is called a glassy texture. An example of an intrusive rock is granite. 2  When magma is above the earth's crust, it is known as lava. 3  Extrusive rocks form through very fast cooling of lava above the Earth's surface. 4  Extrusive rocks have very small, almost microscopic crystals.