How would you expect the stomata of a leaf respond to a drought

The amount of stomata would decrease in response to drought
This is because the stomata are the principal means of gas exchange in the plants. This controls water loss and the exchange of CO2 and Oxygen. 
In drought conditions, excessive evaporation might lead to desiccation and an equally severe disruption of photosynthetic function. Thus, one might expect plant leaves exposed to drought conditions to have fewer stomata in sunlit environments. 

The name of the instrument that the scientist uses is called a microscope.a microscope is used to view objects which is not visible to the naked eyes