{"product_id":"9783848229901","title":"A New Doppler Effect","description":"The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. \u003cbr\u003eIt is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. \u003cbr\u003eThe received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.\u003cbr\u003eThe relative changes in frequency can be explained as follows. \u003cbr\u003eWhen the source of the waves is moving toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave.\u003cbr\u003e Therefore each wave takes slightly less time to reach the observer than the previous wave. \u003cbr\u003eTherefore the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency. \u003cbr\u003eWhile they are travelling, the distance between successive wave fronts is reduced; so the waves \\\\\\\\\\\\\\\"bunch together\\\\\\\\\\\\\\\". \u003cbr\u003eConversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. \u003cbr\u003eThe distance between successive wave fronts is increased, so the waves \"spread out\".\u003cbr\u003eFor waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source is relative to the medium in which the waves are transmitted. \u003cbr\u003eThe total Doppler Effect may therefore result from motion of the source, motion of the observer, or motion of the medium. \u003cbr\u003eEach of these effects is analyzed separately. \u003cbr\u003eFor waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered.","brand":"Books on Demand","offers":[{"title":"Default Title","offer_id":47041446346992,"sku":"9783848229901","price":11.5,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0737\/7593\/9824\/files\/9783848229901_p0.jpg?v=1763696253","url":"https:\/\/shop-qa.barnesandnoble.com\/products\/9783848229901","provider":"Barnes \u0026 Noble (DEV)","version":"1.0","type":"link"}