Introduction to the Microscope

CarePartsFocusing

• An instrument that magnifies or makes tiny objects look bigger

• Two kinds:– Simple – contains only one lens– Compound – two or more

2 set lenses Choice of lens magnification

• This is a compound light microscope.

• It is called this because it has two or more lenses (the eyepiece lenses and the objective lenses), and makes use of light to produce an image.

Mechanism for enlargingan image

Eyepiece

Body Tube

Revolving Nosepiece

ArmObjectives

StageStage Clips

Coarse Focus

Fine Focus

Base

Diaphragm

Light source

Magnification

Supports body tube

Supports slide

Focuses image

Sharpens the image

Supports microscope

Reflects lighttowards eyepiece

Regulatesamount of light

Holds slide In place

Magnification

Hold objective rotates to change magnification

Maintainsproper distancebetween lenses

the eye

the image

the specimen

Each lens magnifies the image, increasing its overall size

A lens is a bi-convex disk that bends light

The farther the light rays are bent, the largerthe image appears

The bent rays produces an image

the eye

the image

the specimen

As the light rays are spread farther apart, the clarity or resolution of the image decreases

Resolving power: A measure of the ability of a lens or optical system to form separate and distinct images of two objects with small angular separation.

Light microscopes are limited in their magnification by their resolving power!

the eye

the image

the specimen

The image is always seen upside down and backwards from its actual position

• Place the Slide on the Microscope

• Use Stage Clips to hold slide in place

• Open the diaphragm (shutter) and switch on the lamp power

• A microscope has several lens and each magnifies the specimen like a magnifying glass

The magnification of the eyepiece is 10 times (10x)

• The two lenses are called:– Eyepiece

– Objective

• The eyepiece has a magnification of “10x”• The magnification of the objective lenses vary

and are marked on the lens• Total magnification =

(Eyepiece) X (Objective)

• Example:

10 X 40 = 400

Ocular lens

Objective lenses

3 objective lens are

4X,

10X and

40X

•Always start with the low power objective (4X)

•Always focus using the coarse knob, then the fine focus knob.

•Centralise what you want further magnified

•Switch to the 10X objective lens and if needed, to the 40X objective lens

• Follow steps to focus using low power

• At high power, use only the fine focus knob!

• Click the nosepiece to the longest objective

• Do NOT use the coarse focusing knob as it will crack the slide.

• Use the fine focus knob to bring the slide

• Do NOT remove the slide as it is very close to the objective lens.

• To remove slide, switch to low-power or mid-power objective lens.

What will you find?

Eyepiece

Arm

Stage

Course adjustment

Fine adjustment

Base

Let’s Review!

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Body tube

Nosepiece

Low power

High power

Stage clips

Diaphragm

Light source

Medium power

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• Always carry with 2 hands – one hand on the arm, the other on the base

• Only use lens paper for cleaning

• Do not force knobs

• Always store covered

• Keep desk clear of objects and cords