[填空题]
A lens appears greenish yel6vl az /6dsc cqarw+36w+q*3ye b+it ulow ($\lambda\;=\;570\;mm$ is strongest) when white light reflects from it. What minimum thickness of coating $(n=1.25)$ do you think is used on such a glass $(n=1.52)$ lens, and why? $t_{min}$ nm
