Final answer:
The two types of filters are active and passive. Active filters require power and can amplify signals, while passive filters like polarizing filters operate on physical properties and do not need power.
Step-by-step explanation:
There are two types of filters: active and passive. Active filters require an external power source to operate, and they can amplify or improve the signal they filter. Passive filters, on the other hand, do not require an external power source and work by removing unwanted frequencies based purely on the physical properties of the circuit components.
For example, a polarizing filter, which is a type of passive filter, is used in photography to reduce glare and reflections. This filter allows light waves of a certain polarization to pass through while blocking others. If you have two polarizing filters, and you rotate one of them, you will see varying amounts of light transmitted through the filters, depending on the angle between their polarization axes. When the axes are perpendicular, no light passes through, which is a practical demonstration of how passive filters can selectively block certain frequencies (or in this case, polarizations of light).