眼睛是心灵的窗户为保护学生视力，启航中学每学期给学生检查视力，下表是该校某班39名学生右眼视力的检查结果，这组视力数据中，中位数是．                                                                                                                                                                                                              

视力	4.0	4.1	4.2	4.3	4.4	4.5	4.6	4.7	4.8	4.9	50
人数	1	2	6	3	3	4	1	2	5	7	5