The Light Source for Meter Stick Optics has a bright green backlit translucent screen with a crossed arrow object. The pattern is asymmetrical so you can tell if the image is reversed and/or inverted. The horizontal and vertical arrows are 2 cm long. The horizontal arrow also includes two lines that are spaced 1 cm apart.
The Light Source fits onto the end of the meter stick and aligns the object with the zero-centimeter mark.
The battery is rechargeable through a USB connection.