You are observing a specimen under the microscope. You have located a cell and brought it into sharp focus using the 10x objective (below left). However, when you switch to the 40x objective, the cell is no longer visible (below right)! What has happened and how would you correct this? [2 pt; G5.2]

The cell was no longer visible because the image wasn't centered before switching to higher objective of 40X.

Explanation:

While using microscopes, the image will approximately remain in focus if you adjust the focus during change of magnification. Therefore, there is need to always adjust the focus during change in magnification.

If object is not centered before switching to a higher power objective, object will not be visible.

To avoid this, center the object before switching to a higher power objective. This will help you find the object after switching the objective. And it is also important to use fine focus and not coarse focus.

When you shift from low power(10x) to high power(40x), the 40X objective lense moves directly over the specimen and this in turns results in the following changes:

•increase in the magnification of a specimen

•decrease in the light intensity which makes the image appears dim

•decrease in the area of field of view, i.e the specimen will appear larger

•decrease in depth of field, i.e. you won't be able to view an entire surface of the specimen.

And the only way to correct this is to shift back to 10X,centre the specimen and then again switch back to 40X

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.