Using magnifying glasses and microscopes
Practical Activity for 14-16
Apparatus and Materials
- Hand lenses
- Microsope, with illuminants and power supply
- Things to look at
Health & Safety and Technical Notes
Microscopes should never be used in a manner which could result in the Sun being imaged; if daylight is used as illumination, ensure the window faces north or away from the Sun.
There should be one hand lens per student and, if possible, a microscope for every four students. Long queues will spoil students' enjoyment of this activity.
Things to look at might include some of the following: sand, salt, blotting-paper, talcum powder, a hair, students' own handwriting, a fingerprint, rocks such as granite, salt dissolving. Prepared slides of blood and a fibrous mineral could also be included if they are available.
- Encourage students to look at anything they want to.
- Get students to begin with their magnifying glasses. It may help to get them to bring the hand lens right up to their eye with one hand. Then they use the other hand to bring the object to be viewed towards the eye. The hand lens could also be supported in a clamp stand.
- Produce the microscopes later. Teach the students to start by looking at the objective lens, from the side, as it is lowered to be near the object to be viewed. Then they look through the eyepiece as the microscope tube is raised, until a clear image is seen. (Students should never lower the microscope as they are bringing the image into focus. The objective lens may crash through the slide!)
- A chief aim of this exercise is for students to become familiar with microscopes so as to be able to use them later just as a tool, rather than a distracting novelty.
- It may also enable students to compare the benefits and disadvantages of using microscopes. They will then be able to decide in other contexts between an adequate magnifying glass and a time-consuming and cumbersome microscope.
This experiment was safety-tested in January 2005