{"type":"rich","version":"1.0","title":"thin-film interference | bubble \"rainbows\" | Feynman QED chapter 1","html":"<iframe src=\"https://www.desmos.com/calculator/vgagjs01ay?embed\" width=\"500px\" height=\"500px\" style=\"border: 1px solid #ccc\" frameborder=0></iframe>","width":500,"height":500}