➜ skills task biology topic 1 cells and tissues how a microscope works ➜ microscopes create a...

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

How a microscope works

➜ Microscopes create a magnified image using lenses.

➜ Light from a lamp is reflected by a mirror (1) up through the specimen on a slide on the stage (2).

➜ The specimen must be thin to let lots of light through.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

How a microscope works

➜ Light passes through the specimen into one of the objective lenses (3).

➜ A magnified image forms inside the microscope’s tube.

➜ The eyepiece lens (4) magnifies this image again.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

How a microscope works

➜ Light passing through the eyepiece lens (4) enters your eye. It forms an image on your retina.

➜ The image can be focused using the focusing knobs (5).

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

Why is the image reversed and upside down?

➜ If you look at a letter e with a microscope it looks like this:

➜ This happens because lenses refract light. ➜ Light rays passing through the specimen cross over

as they go through the objective lens.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

➜ When light rays go though the eyepiece lens they bend but do not cross over.

➜ The upside down and side-to-side image created by the objective lens is just magnified.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

Using a microscope

1. Place the specimen directly over the centre of the hole on the stage (directly over the light).

2. Use clips to hold the slide in place.

3. Adjust the position of the mirror to reflect light up through the stage.

4. If you wear glasses, take them off.

5. Put one eye very close to the eyepiece.

6. Close or cover the other eye.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

How to focus

1. Select the lowest power objective lens. While looking from the side, turn the coarse focus knob to move the stage as close as possible to the objective lens.

2. Make sure the specimen does not hit the objective lens.

Science Progress © Hodder & Stoughton 2014

➜ SKILLS TASK

Biology Topic 1 Cells and tissues

How to focus

3. Look through the eyepiece and focus by slowly turning the coarse focus knob to move the stage away from the objective lens.

4. Once the object comes into view, use the fine focus knob to bring the object into sharp focus.

Science Progress © Hodder & Stoughton 2014