Microscope Basics

Microscope Structure

• The microscope is an instrument designed to make objects visible that are too small to see with the unaided eye.
• It has mechanical and optical parts that work together to magnify objects.

Mechanical Parts

• The draw tube is a hollow cylinder where the eyepiece or ocular is placed.
• The body tube forms the body of the microscope and supports the ocular and draw tube.
• The nosepiece is a circular revolving structure attached to the base of the body tube.
• The dust shield is a metallic structure above the nosepiece that protects the lower lenses.
• The microscope has two focusing knobs: the coarse adjustment knob and the fine adjustment knob.
• The coarse adjustment knob brings the object into view, and the fine adjustment knob is used for sharp focus.
• The illuminator control knob controls the light output of the illuminator.
• The stage is a platform where slides are placed for observation, and it has a circular opening called an aperture.
• The stage has clips or a mechanical device to hold the slide in place.

Carrying the Microscope

• When carrying the microscope, one hand should grasp the arm and the other hand should support the base.
• The base should always be held parallel to the floor.

Optical Parts

• The eyepiece or ocular is a removable cylinder on top of the microscope containing one set of lenses.
• The objective lens gives the initial magnification, with shorter lenses having lower magnification and farther distance from the specimen when focused.
• The microscope may have four objective lenses: scanning lens (4X), low power objective (10X), high power objective (40X), and oil immersion objective (100X).
• The substage condenser is a lens located under the stage aperture, controlling the distance from the stage to condense and focus light on the specimen.
• The iris diaphragm is beneath the condenser, controlling the amount of light passing through the specimen.