positive lens

13 LETTERS · STARTS WITH P

positive lens is a valid 13-letter word worth 17 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

P3O1S1I1T1I1V4E1L1E1N1S1

3 + 1 + 1 + 1 + 1 + 1 + 4 + 1 + 0 + 1 + 1 + 1 + 1 =17 PTS

DOUBLE WORD → 34TRIPLE WORD → 51

MEANING

What does positive lens mean?