What is a high power objective?
The longest objective that is usually used the least. The opposite of a low power objective.
Why is locating an object more difficult if you start with the high-power objective rather than with the low-power objective?
The low power objective is used first for two reasons: First, focusing the low power objective will insure that the other objectives will be at the proper height. Smashing a slide with an objective can damage the objective. Second, you can see a greater area with the low powered objective. This allows you to easily locate an object of interest, center it in frame and then zoom in on it.
The high power objective on a microscope is used anytime you need to achieve greater detail and magnification, and is often used when identifying cells. The high power objective is generally not used in teaching/learning labs as it is usually an oil immersion lens. Using oil means greater cleaning & care is required.
Should you open or close the diaphragm when switching from low power objective to high power objective?
When working with a microscope you should always take procauctions but one question I am asked a lot is When working with a microscope do you open or close the diaphram when working with the medium- and high-power objective nobs? The answer is you keep it open if you don't you won't be abler to see any thing.