While only one patent model for a protractor survives in the Smithsonian collections—from an inventor with a colorful personal history—several of the other objects also provide examples of technical ...

In this required practical activity, it is important to: make, measure and record the angles of incidence accurately using a protractor; observe and use a protractor to measure angles of refraction.

In this required practical activity, it is important to: make, measure and record the angles of incidence accurately using a protractor; observe and use a protractor to measure angles of refraction.