如图,一束光线自介质射向空气,在分界面处发生反射和折射。当入射角为30°时,反射光线和折射光线恰好垂直。则该介质的折射率为( )
A <img src="https://www.beizhujiaoyu.com/uploads/202208/156887466811121.png" alt="" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/156887469529521.png" alt="" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/156887470522151.png" alt="" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/156887471454031.png" alt="" />