Answer:
Well, there can be various causes of not finding any cells while examining a slider under the microscope. Some of them are as follows:
a. The light of the microscope might be switched off and the slide does not comprise any cells.
b. The microscope is not focused appropriately so that one can witness the cells.
c. The region of the slide comprising the cells is not coming in the field of vision.
d. The magnification of the microscope is not appropriate, that is, either it is very low or is very high.
e. Destruction of the sample would have taken place.