[填空题]
A lens appears greenish yell pl;o(bn +fr.u.8*t:ixpekn tslf;pn .d4kokg+o ,+rz4ize( ow ($\lambda\;=\;570\;mm$ 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
