look 既可以作
系动词也可以作
实义动词 作系动词时表示看起来，显得 没有被动，比如 you look fine ，he looks tired
作实义动词时，比如look after ，look down upon 是可以用被动的。
比如He is no longer looked down upon.他不再被看不起了。
The children are well looked after in the kindergarten 孩子们在幼儿园被照顾得很好。
追问那其他的感官动词呢？
追答感官动词 see hear 之类的都可以有被动啊。
He is seen to steal from a shop
he is often heard to sing the song
只有在感官动词当系动词用时无被动，比如看起来，听起来，尝起来等等。