阅读下面两段文字，按要求回答问题。
                                                                                             乡 愁
                                                                                           小时候
                                                                                           乡愁是一枚小小的邮票
                                                                                           我在这头
                                                                                           母亲在那头
                                                                                           长大后
                                                                                          乡愁是一张窄窄的船票
                                                                                          我在这头
                                                                                          新娘在那头
                                                                                          后来啊
                                                                                          乡愁是一方矮矮的坟墓
                                                                                          我在外头
                                                                                          母亲在里头
                                                                                          而现在
                                                                                         乡愁是一湾浅浅的海峡
                                                                                         我在这头
                                                                                        大陆在那头

在探究凸透镜成像的实验中，当烛焰、凸透镜、光屏处于如图所示的位置时，恰能在光屏上得到一个清晰的像．应用这一成像原理的是（　　）

（注：1hm² ＝1公顷）