1. Title: Magnification Lesson Objectives : 1. Can I explain the difference between magnification and resolution? Grade B 2. Can I differentiate between the 2 types of microscopes? Grade C Starter: A drawing lesson….

2. Summer Task: …. Research the difference between magnification and resolution in microscopes. Research the differences between light microscopes and electron microscopes. Extension: There are 2 types of electron microscopes – what are they and which is better?

3. Magnification…. is how much bigger the image is than the actual specimen. How to calculate magnification: length of image length of specimen Magnification = (e.g. x10)

4. Resolution…. is how detailed the image is. Its how well the microscope distinguishes between or separates 2 points that are close together. The higher the resolution, the greater the detail you can see!

5. Resolution continued… How is this achieved by a microscope? Resolution is related to the numerical aperture of the objective lens (the larger the numerical aperture, the better the resolution) and the wavelength of light passing through the lens (the shorter the wavelength, the better the resolution). wavelength of light

6. Light Microscopes…. Number of lenses Lower resolution than an electron microscope (200nm or 0.2µm) Maximum magnification is about x1500. Can you name the parts?

8. Electron microscopes… There are two main types of electron microscope: The transmission electron microscope [TEM]. A beam of electrons passes through the specimen and is dispersed by the structures there. The scattered electrons are then captured on a photographic plate. Only used on thin specimens. The scanning electron microscope [SEM]. The specimen is coated in a very thin layer of metal and a beam of electrons is bounced off the surface onto a photographic plate. This allows 3-D images to be formed. Lower resolution image is given.

9. Differences…. Light microscope TEMSEM Max res0.2µm0.0001µm0.005µm Max mag1500x250 000x100 000x Type of image colouredBlack and white StainsdyesHeavy metals Carbon

10. Staining… Stains are taken up by some parts of the specimen making them darker and therefore a contrast occurs. Light microscopes use methylene blue or eosin. Sectioning – specimens are embedded in wax. Thin sections are cut e.g soft tissue.

11. Plenary….