波长为的单色光垂直照射到置于空气中的玻璃劈尖上，玻璃的折射率为，则第三级暗条纹处的玻璃厚度为（　　）。

A、<img width="24" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/7da3a606-58b4-4c9d-8a4e-3aea79deadc8.png" />

B、<img width="24" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/af6eca86-09fc-4395-a9e9-6f726b98c756.png" />

C、<img width="24" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/0941a041-8850-4193-a22c-09608da280ba.png" />

D、<img width="25" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/8be65053-006d-441b-baba-2c91ee65a18c.png" />