小明用金属铷为阴极的光电管，观测光电效应现象，实验装置示意如图甲所示．已知普朗克常量h=6.63×10﹣34J•s．
Let him _______ a rest. I think he must be tired after the long walk.
The mountain I visited last Sunday isn't very ___________. Few ___________ go sightseeing there.
读3月21日不同纬度地区正午影长示意图（如图），完成以下问题。
