{"product_id":"galvana-mirror-galvanometer","title":"Galvana – The Mirror Galvanometer \/ Beam Turns 2θ Physics Sticker","description":"\u003cp\u003eGalvana, a sea captain of the cable age, reads faint telegraph signals by the swing of a beam of light.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eWilliam Thomson, later Lord Kelvin, developed the mirror galvanometer around the 1858 transatlantic telegraph cable, whose signals were too faint for ordinary needles. A tiny mirror carrying small magnets hangs inside a coil; a current twists it slightly, and a beam of light reflected from it sweeps across a scale. By the law of reflection, turning a mirror by an angle θ turns the reflected beam by twice that angle.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003ebeam deflection = 2θ\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eθ: rotation angle of the mirror (rad)\u003c\/li\u003e\n\u003cli\u003e2θ: rotation angle of the reflected beam (rad)\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eA long light beam acts as a weightless pointer: on a scale a metre away, even a tiny twist of the mirror moves the spot visibly.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e The doubling holds for rotation about an axis in the mirror's plane and perpendicular to the beam's plane. The sensitivity comes from the coil and suspension as well as from the optical lever.\u003c\/p\u003e\u003ch3\u003eOn the sticker\u003c\/h3\u003e\u003cp\u003eGalvana, in a captain's cap, watches a bright beam of light; the mirror and the 2θ angle are not drawn. Printed text: \u003cstrong\u003eGALVANA\u003c\/strong\u003e with the line \u003cstrong\u003eBEAM TURNS 2θ\u003c\/strong\u003e. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"2\" × 2\" \/ White","offer_id":50964044382311,"sku":"25846951362040325246","price":4.99,"currency_code":"USD","in_stock":true},{"title":"3\" × 3\" \/ White","offer_id":50964044415079,"sku":"12080743568057716204","price":6.99,"currency_code":"USD","in_stock":true},{"title":"4\" × 4\" \/ White","offer_id":50964044447847,"sku":"88928112988668013266","price":8.99,"currency_code":"USD","in_stock":true},{"title":"6\" × 6\" \/ White","offer_id":50964044480615,"sku":"20364042727770499770","price":11.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/17653096386954176330_1200.jpg?v=1793658803","url":"https:\/\/pixelatedphysics.com\/nl\/products\/galvana-mirror-galvanometer","provider":"Pixelated Physics","version":"1.0","type":"link"}