{"product_id":"the-periscope-beyond-looking-around-corners","title":"The Periscope Beyond Looking Around Corners","description":"\u003ch3 data-start=\"830\" data-end=\"866\" class=\"PDq2pG_selectionAnchorContainer\"\u003eA periscope lets you see over walls.\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h3\u003e\n\u003ch3 data-start=\"868\" data-end=\"918\"\u003eBut what happens if you rotate one of its mirrors?\u003c\/h3\u003e\n\u003ch3 data-start=\"920\" data-end=\"951\"\u003eDoes the image remain the same?\u003c\/h3\u003e\n\u003ch3 data-start=\"953\" data-end=\"994\"\u003eOr does the entire world begin to rotate?\u003c\/h3\u003e\n\u003ch3 data-start=\"996\" data-end=\"1127\"\u003eThis experiment reveals that a periscope is much more than a viewing tube—it is a device that transforms images in surprising ways.\u003c\/h3\u003e\n\u003ch1 data-section-id=\"l9fb4n\" data-start=\"1134\" data-end=\"1164\" class=\"PDq2pG_selectionAnchorContainer\"\u003eBuilding the First Periscope\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"1166\" data-end=\"1188\"\u003eThe first design used:\u003c\/p\u003e\n\u003cul data-start=\"1190\" data-end=\"1259\"\u003e\n\u003cli data-section-id=\"19sq57n\" data-start=\"1190\" data-end=\"1213\"\u003eOne straight PVC pipe\u003c\/li\u003e\n\u003cli data-section-id=\"1phjtny\" data-start=\"1214\" data-end=\"1239\"\u003eTwo L-shaped PVC joints\u003c\/li\u003e\n\u003cli data-section-id=\"1v6o8l4\" data-start=\"1240\" data-end=\"1259\"\u003eTwo plane mirrors\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-start=\"1261\" data-end=\"1296\"\u003eEach elbow was cut with a 45° slot.\u003c\/p\u003e\n\u003cp data-start=\"1298\" data-end=\"1414\"\u003eThe mirrors were trimmed using a glass cutter and inserted into these slots so that each mirror was inclined at 45°.\u003c\/p\u003e\n\u003cp data-start=\"1416\" data-end=\"1501\"\u003eAfter assembling the elbows onto the straight pipe, a working periscope was obtained.\u003c\/p\u003e\n\u003cp data-start=\"1503\" data-end=\"1588\"\u003eBecause the elbows could rotate independently, this became a \u003cstrong data-start=\"1564\" data-end=\"1587\"\u003erotatable periscope\u003c\/strong\u003e.\u003c\/p\u003e\n\u003ch1 data-section-id=\"100ndmw\" data-start=\"1595\" data-end=\"1635\" class=\"PDq2pG_selectionAnchorContainer\"\u003eObservation 1 — The Ordinary Periscope\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"1637\" data-end=\"1728\"\u003eWith both mirrors in the usual orientation, the distant scene appeared exactly as expected.\u003c\/p\u003e\n\u003cp data-start=\"1730\" data-end=\"1795\"\u003eThe observer could look over obstacles without changing position.\u003c\/p\u003e\n\u003cp data-start=\"1797\" data-end=\"1857\"\u003eThe light underwent two reflections before reaching the eye.\u003c\/p\u003e\n\u003ch1 data-section-id=\"7fmkmb\" data-start=\"1864\" data-end=\"1901\" class=\"PDq2pG_selectionAnchorContainer\"\u003eObservation 2 — Rotating One Mirror\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"1903\" data-end=\"1932\"\u003eOne elbow was rotated by 45°.\u003c\/p\u003e\n\u003cp data-start=\"1934\" data-end=\"1969\"\u003eThe same object was observed again.\u003c\/p\u003e\n\u003cp data-start=\"1971\" data-end=\"2021\"\u003eThe image itself had rotated by approximately 45°.\u003c\/p\u003e\n\u003cp data-start=\"2023\" data-end=\"2048\"\u003eNothing else had changed.\u003c\/p\u003e\n\u003cp data-start=\"2050\" data-end=\"2085\"\u003eOnly the orientation of one mirror.\u003c\/p\u003e\n\u003cp data-start=\"2087\" data-end=\"2135\"\u003eThis immediately raises an interesting question:\u003c\/p\u003e\n\u003cp data-start=\"2137\" data-end=\"2193\"\u003e\u003cstrong data-start=\"2137\" data-end=\"2193\"\u003eHow can rotating one mirror rotate the entire image?\u003c\/strong\u003e\u003c\/p\u003e\n\u003ch1 data-section-id=\"11xvdd7\" data-start=\"2200\" data-end=\"2236\" class=\"PDq2pG_selectionAnchorContainer\"\u003eObservation 3 — Looking Behind You\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"2238\" data-end=\"2303\"\u003eThe elbow was rotated further until the periscope faced backward.\u003c\/p\u003e\n\u003cp data-start=\"2305\" data-end=\"2349\"\u003eNow an even more surprising effect appeared.\u003c\/p\u003e\n\u003cp data-start=\"2351\" data-end=\"2395\"\u003eThe image had rotated by approximately 180°.\u003c\/p\u003e\n\u003cp data-start=\"2397\" data-end=\"2463\"\u003eThe periscope was no longer simply changing the viewing direction.\u003c\/p\u003e\n\u003cp data-start=\"2465\" data-end=\"2522\"\u003eIt was also changing the orientation of the image itself.\u003c\/p\u003e\n\u003cp data-start=\"2524\" data-end=\"2638\"\u003eThis behaviour can be understood by carefully tracing how successive reflections transform the direction of light.\u003c\/p\u003e\n\u003ch1 data-section-id=\"skturq\" data-start=\"2645\" data-end=\"2668\" class=\"PDq2pG_selectionAnchorContainer\"\u003eWhy Does This Happen?\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"2670\" data-end=\"2757\"\u003eEach mirror changes the direction of incoming light according to the law of reflection.\u003c\/p\u003e\n\u003cp data-start=\"2759\" data-end=\"2861\"\u003eWhen the orientation of one mirror changes, the relationship between the two reflections also changes.\u003c\/p\u003e\n\u003cp data-start=\"2863\" data-end=\"2926\"\u003eThe final image therefore undergoes a geometric transformation.\u003c\/p\u003e\n\u003cp data-start=\"2928\" data-end=\"2981\"\u003eThe periscope becomes a beautiful demonstration that:\u003c\/p\u003e\n\u003cblockquote data-start=\"2983\" data-end=\"3096\"\u003e\n\u003cp data-start=\"2985\" data-end=\"3096\"\u003e\u003cstrong data-start=\"2985\" data-end=\"3096\"\u003eChanging the orientation of optical elements changes not only where we look, but also how we see the scene.\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/blockquote\u003e\n\u003cp data-start=\"3098\" data-end=\"3166\"\u003eThis is an invitation to explore ray tracing and geometrical optics.\u003c\/p\u003e\n\u003ch1 data-section-id=\"1rgrm71\" data-start=\"3173\" data-end=\"3204\" class=\"PDq2pG_selectionAnchorContainer\"\u003eBuilding the Second Periscope\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"3206\" data-end=\"3245\"\u003eA second design focused on versatility.\u003c\/p\u003e\n\u003cp data-start=\"3247\" data-end=\"3300\"\u003eTwo sheets of chart paper were rolled into cylinders.\u003c\/p\u003e\n\u003cp data-start=\"3302\" data-end=\"3346\"\u003eOne cylinder slid smoothly inside the other.\u003c\/p\u003e\n\u003cp data-start=\"3348\" data-end=\"3388\"\u003eThis created an extendable viewing tube.\u003c\/p\u003e\n\u003cp data-start=\"3390\" data-end=\"3445\"\u003eTwo folded cardboard cuboids were attached to the ends.\u003c\/p\u003e\n\u003cp data-start=\"3447\" data-end=\"3486\"\u003eEach contained a mirror mounted at 45°.\u003c\/p\u003e\n\u003cp data-start=\"3488\" data-end=\"3563\"\u003eCircular openings allowed the cylindrical tube to pass through the cuboids.\u003c\/p\u003e\n\u003cp data-start=\"3565\" data-end=\"3603\"\u003eThe result was a periscope that could:\u003c\/p\u003e\n\u003cul data-start=\"3605\" data-end=\"3693\"\u003e\n\u003cli data-section-id=\"1b3uviq\" data-start=\"3605\" data-end=\"3635\"\u003eExtend to different heights.\u003c\/li\u003e\n\u003cli data-section-id=\"j3z8pr\" data-start=\"3636\" data-end=\"3660\"\u003eRotate about its axis.\u003c\/li\u003e\n\u003cli data-section-id=\"tx87he\" data-start=\"3661\" data-end=\"3693\"\u003eBe collapsed for easy storage.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch1 data-section-id=\"fmkelf\" data-start=\"4095\" data-end=\"4112\" class=\"PDq2pG_selectionAnchorContainer\"\u003eReal-World Uses\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"4114\" data-end=\"4184\"\u003ePeriscopes have been used wherever direct line of sight is impossible.\u003c\/p\u003e\n\u003cp data-start=\"4186\" data-end=\"4203\"\u003eExamples include:\u003c\/p\u003e\n\u003cul data-start=\"4205\" data-end=\"4355\"\u003e\n\u003cli data-section-id=\"dccmxg\" data-start=\"4205\" data-end=\"4252\"\u003eSubmarines observing above the water surface.\u003c\/li\u003e\n\u003cli data-section-id=\"yoydfe\" data-start=\"4253\" data-end=\"4273\"\u003eArmoured vehicles.\u003c\/li\u003e\n\u003cli data-section-id=\"bubuhb\" data-start=\"4274\" data-end=\"4294\"\u003eObservation posts.\u003c\/li\u003e\n\u003cli data-section-id=\"1vhgwiv\" data-start=\"4295\" data-end=\"4331\"\u003eInspection of inaccessible spaces.\u003c\/li\u003e\n\u003cli data-section-id=\"6zqslr\" data-start=\"4332\" data-end=\"4355\"\u003eIndustrial machinery.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-start=\"4357\" data-end=\"4479\"\u003eAlthough many modern systems now use cameras and electronic displays, the underlying geometric principle remains the same.\u003c\/p\u003e\n\u003ch1 data-section-id=\"qu0os0\" data-start=\"4931\" data-end=\"4953\" class=\"PDq2pG_selectionAnchorContainer\"\u003eA Deeper Realization\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp data-start=\"4955\" data-end=\"5026\"\u003eThe remarkable feature of a periscope is that \u003cstrong data-start=\"5001\" data-end=\"5025\"\u003eit never bends light\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp data-start=\"5028\" data-end=\"5079\"\u003eEvery ray still obeys the simple law of reflection.\u003c\/p\u003e\n\u003cp data-start=\"5081\" data-end=\"5211\"\u003eYet by combining two mirrors in different orientations, we can completely change where we look and even rotate the apparent world.\u003c\/p\u003e\n\u003cp data-start=\"5213\" data-end=\"5323\"\u003eComplex optical instruments are often built from surprisingly simple components arranged in clever geometries.\u003c\/p\u003e\n\u003ch3 data-section-id=\"6yv1zy\" data-start=\"1882\" data-end=\"1912\" class=\"PDq2pG_selectionAnchorContainer\"\u003eContinue the Investigation\u003cspan aria-hidden=\"true\" class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h3\u003e\n\u003cp data-start=\"1914\" data-end=\"2111\"\u003eThe experiment you've just explored is only the beginning. Our hands-on investigation sets are designed to help you recreate, extend, and deepen these ideas through observation and experimentation.\u003c\/p\u003e\n\u003cp data-start=\"2113\" data-end=\"2369\"\u003eEvery investigation has the potential to lead to a new question. If you discover something interesting, improve the experiment, or develop a new variation, share it with the Geometers community. Your work may inspire others and could even be featured here.\u003c\/p\u003e\n\u003cp data-start=\"2371\" data-end=\"2430\"\u003e\u003cstrong data-start=\"2371\" data-end=\"2430\"\u003eKeep experimenting. Keep questioning. Keep discovering.\u003c\/strong\u003e\u003c\/p\u003e","brand":"Geometers","offers":[{"title":"Default Title","offer_id":46251048829064,"sku":null,"price":499.0,"currency_code":"INR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0725\/3891\/4952\/files\/1_df2b29ee-f5c6-4f73-92fb-6506ee9d629c.jpg?v=1785214611","url":"https:\/\/geometers.in\/products\/the-periscope-beyond-looking-around-corners","provider":"Geometers","version":"1.0","type":"link"}