{"product_id":"the-ionospheric-mirror-plate-076-physics-poster","title":"The Ionospheric Mirror – Plate 076 Physics Poster","description":"\u003cp\u003ePlate 76 speaks for itself: \u003cem\u003e“Below about 9 MHz on a typical day, the sky is a mirror.”\u003c\/em\u003e\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eRadio waves below the plasma frequency of the ionosphere's F2 layer cannot propagate in it and are reflected back. Appleton and Barnett proved the layer exists in 1924.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003ef_p ≈ 8.98 √n_e Hz\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003ef_p: plasma frequency, Hz\u003c\/li\u003e\n\u003cli\u003en_e: electron density, m⁻³\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eF2 layer, n_e ~ 10¹² m⁻³, gives ≈ 9 MHz. Appleton \u0026amp; Barnett showed it, 11 Dec 1924.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e The critical frequency ranges from about 2 to 15 MHz with time of day, season and solar cycle, and applies to waves sent straight up; oblique waves reflect at higher frequencies.\u003c\/p\u003e\u003ch3\u003eSources\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eE. V. Appleton, M. A. F. Barnett, Nature 115, 333 (1925).\u003c\/li\u003e\n\u003cli\u003eK. Davies, Ionospheric Radio (1990).\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eOn the poster\u003c\/h3\u003e\u003cp\u003ePlate 076, “The Ionospheric Mirror”: the pixel-art plate with its slogan “Below about 9 MHz on a typical day, the sky is a mirror.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.\u003c\/p\u003e","brand":"Pixelated Physics","offers":[{"title":"9'' x 12\" (Vertical) \/ Matte","offer_id":50962673893479,"sku":"67517751052901965244","price":19.99,"currency_code":"USD","in_stock":true},{"title":"9'' x 12\" (Vertical) \/ Fine Art","offer_id":50962673926247,"sku":"75060504543929920828","price":29.99,"currency_code":"USD","in_stock":true},{"title":"9'' x 12\" (Vertical) \/ Semi Glossy","offer_id":50962673959015,"sku":"28568115249563350410","price":19.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Fine Art","offer_id":50962673991783,"sku":"11406209215348460495","price":44.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Semi Glossy","offer_id":50962674024551,"sku":"32934969880961106506","price":29.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Matte","offer_id":50962674057319,"sku":"51172000657932726701","price":29.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Matte","offer_id":50962674090087,"sku":"18348227489270686182","price":69.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Fine Art","offer_id":50962674122855,"sku":"17856328930615074309","price":119.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Semi Glossy","offer_id":50962674155623,"sku":"41168622071416396402","price":69.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/16465705686209715938_2048.jpg?v=1793734218","url":"https:\/\/pixelatedphysics.com\/nl\/products\/the-ionospheric-mirror-plate-076-physics-poster","provider":"Pixelated Physics","version":"1.0","type":"link"}