A recent query from a friend reminded me that some topics are both very easy and very hard to grasp at the same time. The key is often in the way we look at the it. He asked “Why does a mirror NOT invert images top-to-bottom?”\u00a0 Or better yet, why DOES a mirror invert images left-to-right? I used to ask this question to my undergraduate students in my Modern Optics class at UT when teaching them basic imaging equations. None of them ever answered the question correctly. But the answer, it turns out, is simple.\u00a0 \u00a0Mirrors don’t invert anything.\u00a0 You do, and not with your brain.<\/p>\n\n\n\n
Try this experiment.\u00a0 Go up to a mirror with an open book in your hand.\u00a0 Look at the printing – obviously it is perfectly readable.\u00a0 Now turn the book to face the mirror – you see that all of the writing in the mirror is inverted, going from right to left instead of left to right.\u00a0 What caused\u00a0that?\u00a0 You did, when you TURNED the book.\u00a0 Don’t believe me?\u00a0 Repeat\u00a0the experiment with an overhead transparency (yes, I am old enough to know what those\u00a0are).\u00a0 Write a word on the overhead transparency and hold it up to the mirror.\u00a0 It is not inverted, when looking at it either directly or in the mirror.\u00a0 When you turn the transparency to face the mirror, the word is inverted when viewed both directly and in the mirror.<\/p>\n\n\n\n
When you look at yourself in the mirror and wave your right hand, it looks like your mirror image is waving their left hand. But that is because we imagine ourselves turned around and facing the other way. Again, it the turning (or imaging that we turned) that does the inverting, not the mirror.<\/p>\n\n\n\n
Mystery solved.<\/p>\n","protected":false},"excerpt":{"rendered":"
A recent query from a friend reminded me that some topics are both very easy and very hard to grasp at the same time. The key is often in the way we look at the it. He asked “Why does a mirror NOT invert images top-to-bottom?”\u00a0 Or better yet, why DOES a mirror invert images […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-662","post","type-post","status-publish","format-standard","hentry","category-general"],"_links":{"self":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/662","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=662"}],"version-history":[{"count":1,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/662\/revisions"}],"predecessor-version":[{"id":663,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/662\/revisions\/663"}],"wp:attachment":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=662"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=662"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}