TOPIC:

ID Code: M5-23
Purpose: White light interference from Lloyd's mirror.
Description: More fringes can be shown with a laser, but it is interesting to show that ordinary white light does interfere. Lloyd's mirror shows fewer "extraneous" diffraction effects than other wave-front splitting interferometers. An important point here is to show that a phase change occurs on reflection from the glass surface of the mirror. This is hard to show because the center (plane of mirror) is difficult to determine. However, it is shown indirectly by the sequence of colors in the white light fringes: the first easily visible color separation is the first order dark fringe, red-black-blue going away from the center.

White light fringes are shown in the photograph at the left below and the close-up in the center. Placing a red fileter in the light path allows you to see more fringes by only using a narrow band of red light. The actual pattern seen with the eye is considerably better than that displayed by the video, increasing visibility to several lines.

Projection on a ground glass screen is bright and pretty for individual viewing. Projection on large screen is dim and hard to see from distance. The color minicam with TV projector can be used for large groups.

Availability: Available