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

Slide 1 / 17 Slide 2 / 17 Structure and Function, & Information Processing Lab 1: Investigating Cells Intro to Microscopes www.njctl.org Slide 3 / 17 Slide 4 / 17 Microscopes - a bit of history Microscopes - a bit of history In 1665 Robert Hooke, an English Physicist, sliced up a cork and Was Hooke looking at actual cells - the fundamental units of life? 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 Technically, cork is made out of wood, which comes from trees, squares that reminded him of the "cells" Monks lived in at which are living organisms, so yes...they were just dead cells. monasteries. Slide 5 / 17 Slide 6 / 17 Microscopes - a bit of history Microscopes - a bit of history Dutch scientist Anton van Leeuwenhoek is considered to be the father His favorite party trick was to invite people over for dinner, of microscopy. In 1664 he started designing more sophisticated have them scrape their teeth with a pick, and then look at the powerful microscopes. microorganisms from their mouth under the lens. These were the days before toothpaste. He looked at everything under a microscope - blood, pond water, insects, phlegm, etc. - and made elaborate drawings of what he saw.

Slide 7 / 17 Slide 8 / 17 Compound Light Microscope Compound Light Microscope Compound Light Microscopes are the microscopes commonly used in schools. Bright bulb that illuminates specimen. They have a a built-in light source and two lenses that magnify well-lit objects and bring them into focus. Slide 9 / 17 Slide 10 / 17 Compound Light Microscope Compound Light Microscope Objective lenses magnify The Ocular Lens is the your image: part you look through, 4x - small and it magnifies 10x - medium already magnified objects 10x more. 40x - large 100x - largest, you must use oil if you use this one. Slide 11 / 17 Slide 12 / 17 How to Use a Microscope How to Use a Microscope 1. Use Coarse 3. Turn on light and Adjustment Knob to rotate objectives so that Lower the stage as low the smallest, 4x lens, is as possible. in place above the specimen (you will feel it catch when it's right). 2. Place slide with specimen centered on 4. Look through the the stage, over the light Ocular Lens and use source, and clip it in. the Coarse Adjustment Knob to slowly raise the stage until the specimen comes into clear view. STOP

Slide 13 / 17 Slide 14 / 17 How to Use a Microscope 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 . 7. If the image is too dark, 5. Use the Fine adjust the diaphragm to Adjustment Knob to let more light in. focus the image. 6. For higher magnification, adjust the objective lenses, but leave the stage as is and use Fine Adjustment Knob to focus the image. Slide 15 / 17 Slide 15 (Answer) / 17 1 You are looking at a specimen under the microscope 1 You are looking at a specimen under the microscope using the low power, 4x objective. If your ocular lens using the low power, 4x objective. If your ocular lens has a magnification power of 10x and your objective has a magnification power of 10x and your objective lens has a magnification power of 4x, what is the lens has a magnification power of 4x, what is the total magnification of your specimen? total magnification of your specimen? Answer 40x [This object is a pull tab] Slide 16 / 17 Slide 16 (Answer) / 17 2 What is the total magnification of an object viewed 2 What is the total magnification of an object viewed using a 10x ocular lens and a 10x objective lens? using a 10x ocular lens and a 10x objective lens? Answer 100x [This object is a pull tab]

Slide 17 / 17 Slide 17 (Answer) / 17 Using a standard compound light microscope with a Using a standard compound light microscope with a 3 3 10x ocular lens, a specimen is viewed at 400x 10x ocular lens, a specimen is viewed at 400x magnification. Which objective lens was used? magnification. Which objective lens was used? A 4x A 4x B 10x B 10x Answer C C 40x C 40x D 400x D 400x [This object is a pull tab]