What must be rotated to switch from low to high power objective?

If a microscope has a 4x ocular lens and a 10x objective, what is the microscope's total magnification?

Why it is necessary for the specimen to be thin so it can be observed under the microscope?

When you view a specimen through an objective lens that is magnified 40X,what is the actual magnification?

What part of the microscope can increase or decrease the amount of light entering the stage opening?