Making a Spectacle: Practicals

Six practicals produced by the Institute of Physics (IOP) that help students to understand the electromagnetic spectrum and about materials used in making spectacles.

In addition to the guidance included for specific activities, please refer to the generic health and safety information before commencing any practical activity.

These resources are accompanied by the Teacher and technicians' guide for both the practicals and activity sheets.

Spring surprise
This series of activities is suitable for a foundation and higher tier classes.They explore the properties of a smart material, Nitinol, to sharpen up their concepts of scientific theory, evidence and proof. With all the writing up, the activities could last an hour.

Sudden changes
The main practical activity involves the use of: resistance = voltage/current to provide evidence for a hypothesis about a shape-memory alloy called Nitinol.Careful measurement is required for the resistance change to appear, so this activity is aimed at higher tier classes.The suggested plenary demonstration could make the activity last an hour.

Seeing the light
This work introduces students to how lenses work through a practical investigation of the use of spectacles to improve vision.They can be asked to collect old spectacles from friends or relatives, or from a local optician.They can be instructed to ask what the spectacles have been used for. Avoid vari-focal lenses. Students should have been introduced to basic concepts including how rays of light travel in straight lines and the refraction of light at air/glass surfaces before commencing this work. Some advice on drawing ray diagrams is also necessary.

Invisible waves
These experiments emulate the work of Herschel and Ritter. A glass prism is used to disperse sunlight and students are asked to explain observations of the formation of the white light spectrum using the terms dispersion, refraction, speed and colour.This could be done as a research exercise to introduce the topics or as revision.

Ultra-violent light?
The two investigations allow students to investigate the action of polarising lenses and UV filters in sunglasses.They can be used to develop and consolidate understanding of waves and wavelengths. It may come as a surprise that the UV filter is colourless and this could form the basis of a class discussion.

Correcting lenses
This simple model uses two lenses to represent the cornea and the crystalline lens of the eye. Changing the power of the lens representing the eye lens, but retaining the lens representing the cornea,models the fixed nature of the cornea and the ability of the crystalline lens to change power to focus images between 8 cm and infinity.

• URL: http://stem.org.uk/rxhx