A tank filled with Karo syrup is placed between two crossed Polaroids to demonstrate optical activity. As polarized light passes through the syrup, the plane of polarization is rotated due to the syrup's optically active properties. The amount of rotation depends on the concentration of the syrup and the wavelength of light. When viewed through the second Polaroid, the light emerging from the syrup tank displays vivid colors that change as the Polaroid is rotated, illustrating the wavelength-dependent rotation of polarized light.