Lab 1: Investigating Cells Intro to Microscopes www.njctl.org - - PDF document

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Lab 1: Investigating Cells Intro to Microscopes

www.njctl.org

Structure and Function, & Information Processing Slide 3 / 17 Microscopes - a bit of history

In 1665 Robert Hooke, an English Physicist, sliced up a cork and looked at it under an early miscroscope that was just some magnifying lenses stacked on top of each other in a tube. Hooke noticed that the cork looked like it was made up of tiny squares that reminded him of the "cells" Monks lived in at monasteries.

Slide 4 / 17 Microscopes - a bit of history

Was Hooke looking at actual cells - the fundamental units of life? Technically, cork is made out of wood, which comes from trees, which are living organisms, so yes...they were just dead cells.

Slide 5 / 17 Microscopes - a bit of history

Dutch scientist Anton van Leeuwenhoek is considered to be the father

• f microscopy. In 1664 he started designing more sophisticated

powerful microscopes. He looked at everything under a microscope - blood, pond water, insects, phlegm, etc. - and made elaborate drawings of what he saw.

Slide 6 / 17 Microscopes - a bit of history

His favorite party trick was to invite people over for dinner, have them scrape their teeth with a pick, and then look at the microorganisms from their mouth under the lens. These were the days before toothpaste.

Slide 7 / 17 Compound Light Microscope

Compound Light Microscopes are the microscopes commonly used in schools. They have a a built-in light source and two lenses that magnify well-lit objects and bring them into focus.

Slide 8 / 17 Compound Light Microscope

Bright bulb that illuminates specimen.

Slide 9 / 17 Compound Light Microscope

Objective lenses magnify your image: 4x - small 10x - medium 40x - large 100x - largest, you must use oil if you use this one.

Slide 10 / 17 Compound Light Microscope

The Ocular Lens is the part you look through, and it magnifies already magnified

• bjects 10x more.

Slide 11 / 17 How to Use a Microscope

• 1. Use Coarse

Adjustment Knob to Lower the stage as low as possible.

• 2. Place slide with

specimen centered on the stage, over the light source, and clip it in.

Slide 12 / 17 How to Use a Microscope

• 3. Turn on light and

rotate objectives so that the smallest, 4x lens, is in place above the specimen (you will feel it catch when it's right).

• 4. Look through the

Ocular Lens and use the Coarse Adjustment Knob to slowly raise the stage until the specimen comes into clear view. STOP

Slide 13 / 17 How to Use a Microscope

If your specimen is in clear view, the stage is set, so don't touch the Coarse Adjustment Knob again.

• 5. Use the Fine

Adjustment Knob to focus the image.

• 6. For higher

magnification, adjust the

• bjective lenses, but leave

the stage as is and use Fine Adjustment Knob to focus the image.

Slide 14 / 17 How to Use a Microscope

• 7. If the image is too dark,

adjust the diaphragm to let more light in.

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1 You are looking at a specimen under the microscope using the low power, 4x objective. If your ocular lens has a magnification power of 10x and your objective lens has a magnification power of 4x, what is the total magnification of your specimen?

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1 You are looking at a specimen under the microscope using the low power, 4x objective. If your ocular lens has a magnification power of 10x and your objective lens has a magnification power of 4x, what is the total magnification of your specimen?

[This object is a pull tab]

Answer 40x

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2 What is the total magnification of an object viewed using a 10x ocular lens and a 10x objective lens?

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2 What is the total magnification of an object viewed using a 10x ocular lens and a 10x objective lens?

[This object is a pull tab]

Answer 100x

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3 A 4x B 10x C 40x D 400x Using a standard compound light microscope with a 10x ocular lens, a specimen is viewed at 400x

• magnification. Which objective lens was used?

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3 A 4x B 10x C 40x D 400x Using a standard compound light microscope with a 10x ocular lens, a specimen is viewed at 400x

• magnification. Which objective lens was used?

[This object is a pull tab]

Answer C