In this presentation you will: explore the importance and use of light microscopes Introduction to the Microscope Next >

Introduction Many things that are known and understood today, could not have been discovered without microscopes. This is especially the case with the life sciences. Microscopes are used to magnify things that are too small to be seen clearly by the naked eye. Next > For example, without the microscope we would never have found out that all living things are made from cells.

"Microscopes are used to magnify things that are too small to be seen clearly by the naked eye." Is this statement true or false? Question 1 Answer True or False. Next >

"Microscopes are used to magnify things that are too small to be seen clearly by the naked eye." Is this statement true or false? Question 1 Answer True or False. True Next >

Parts of the Light Microscope 1.Eye Piece/ Ocular 2.Arm 3. Low Power Objective 4. Stage Clips 5. Coarse Focus Adjustment 6. Fine Focus Adjustment 7. Revolving Nose Piece 8. High Power Objective 9. Stage 10. Diaphragm 11. Aperture 12. Light/ Mirror 13. Base

Next > Function Arm Coarse focus adjustment Stage Clips Eye piece Eye piece - magnifies objects Support arm - holds the lenses in position over the stage Revolving nose piece Rotating nose piece - for changing objective lenses Clips - to secure specimen slide to the stage Coarse focus dial - for focusing and large movements of the stage

Next > Function Stage Base Diaphragm dial Fine Focus Adjustment Light/ mirror Stage - for supporting specimen slide Diaphragm dial - adjusts the amount of light that shines on to the slide Fine focus dial - for focusing and small movements of the stage Base - weighted to keep microscope stable This directs the light upward onto the slide.

Low Power Objective – a small lens with low magnifying power. High-Power objective – A large lens with high magnifying power. Aperture- hole or an opening through which light travels

Next > What is the purpose of the diaphragm dial on a light microscope? Question 2 A) To magnify the specimen B) To hold the glass slide in place C) To change the objective lens being used D) To adjust the amount of light that is directed through the specimen

What is the purpose of the diaphragm dial on a light microscope? Question 2 A) To magnify the specimen B) To hold the glass slide in place C) To change the objective lens being used D) To adjust the amount of light that is directed through the specimen Next >

Guidelines for Using the Light Microscope Microscopes are expensive precision instruments and must be handled with care. Keep the instrument in a box or under a cover when not in use. Use only the supporting arm of the microscope to lift it. Always carry the microscope with one hand underneath the base and the other hand holding the supporting arm.

Next > Guidelines for Using the Light Microscope Keep the lenses clean by wiping them with lens tissue. Never touch the lenses with your fingers. Always handle microscope slides by their edges.

Next > Total Magnification The total magnification of an image is equal to the magnifying power of the eye piece lens multiplied by the magnifying power of the objective lens. Eye piece Objective lens

Next > Total Magnification The magnifying power of each lens is usually inscribed on the lens barrel. For example, if a ×10 objective lens is used, assuming the eye piece magnification is ×10, the total magnification of the image will be (×10) × = × 100. Eye piece Objective lens

Next > Selecting the Lowest Power Objective Lens To do this, position the ×4 objective lens so that it lies directly above the hole in the stage. It is normal practice to look at a specimen using the lowest available magnification first, then to look more closely at the specimen using a higher magnification.

Next > Placing the Slide on the Stage Before you place a slide on the stage, use the coarse focus dial to position the stage of the microscope so that there is at least a 2 cm gap between the objective lens and the stage. Place the slide on the stage, so that the specimen is over the middle of the hole on the stage.

Next > Placing the Slide on the Stage Make sure that light is shining through the slide, and then secure it in place with the clips. This will help to prevent the slide from being dislodged when you are viewing it.

Next > Raising the Stage Looking at the stage and the slide from the side, use the coarse focus dial to raise the stage so that it is as close to the objective lens as possible without the risk of damaging the slide.

Next > Getting the Specimen into Focus Looking through the microscope eye piece, use the coarse focus dial to slowly move the stage downward. Do this until the specimen comes into focus.

Next > Getting the Specimen into Focus Try to keep both eyes open as you do this, as it will help to prevent eye strain and headaches. Never move the stage upward when you are looking through the microscope eye piece. This is because, when using the higher powered objective lenses, you can easily crush the slide and break the lens.

Next > Minor Focusing Adjustments The fine focus dial alters the height of the stage more accurately than the coarse focus dial. You may need to make minor adjustments to the height of the stage using the fine focus dial to get your specimen into sharp focus.

Next > Adjusting the Diaphragm Dial The diaphragm dial can be rotated to let different amounts of light through the specimen. Finding the amount of light that produces the best viewing results for each specimen is often a matter of trial and error.

Next > What part of the microscope is used to make minor focusing adjustments? Question 3 A) The diaphragm B) The coarse focusing dial C) The fine focusing dial D) The objective lens

What part of the microscope is used to make minor focusing adjustments? Question 3 A) The diaphragm B) The coarse focusing dial C) The fine focusing dial D) The objective lens Next >

Biological Drawings It is good practice to make biological drawings of what you see using a microscope. The aim of a biological drawing is to provide a clear, labeled account of what you have seen.

Next > Biological Drawings Biological drawings are useful because they: allow you to study a specimen in detail provide a clear, labeled account of what you have seen act as a memory aid to help you remember what you have seen

Next > Which of the following states why it is useful to make biological drawings from things you see using a microscope? Question 4 A) To provide a clear, labeled account of what you have seen B) To help you to remember what you have seen C) To allow you to study the specimen in detail D) All of the above

Next > Which of the following states why it is useful to make biological drawings from things you see using a microscope? Question 4 A) To provide a clear, labeled account of what you have seen B) To help you to remember what you have seen C) To allow you to study the specimen in detail D) All of the above

Summary In this presentation you have seen: End > the purpose of microscopes how a light microscope should be used why biological drawings are used