path different = nλ
我想知呢條公式應該係搵constuctive/destuctive
但我唔係好明就係 有時候就咁睇既只係直接path different 相減
e.g AB-CB = 2-1= 1λ~~咁就知道係constuctive( in phase)
但係有時又要path different /λ
e.g AB-CB = 2.55 , 2.55/1.7 = 1.5 , 就係搵個n (λ=1.7)
咁究竟搵constuctive/destuctive
係唔係有2種方法???
path differenth的問題
2009-03-10 7:31 am
回答 (2)
2009-03-11 3:18 am
✔ 最佳答案
the key point is to determine the value of N (if the source are in phase)in case 1, the path difference is expressed as multiple of wave length, so n can be determine directly (2λ- λ = λ, so n = 1)
in case 2, the path difference is expressed as metric unit, so you have to divide the metric path difference with the wave length.
You can check your question to confirm this.
2009-03-10 8:08 am
其實兩個例子都係一樣計 path difference（要注意係 "AB 同 BC 相減" 而不是 "path difference" 相減，AB 同 BC 既 difference 就係 path difference）
path difference = kλ 同 (path difference)/λ = k 係同一樣野黎架，計到 k 係 integer (n) 就係 constructive，k 係一個 integer + 1/2 (n + 1/2) 就係 destructive [當然個 source 要 coherent]
path difference = kλ 同 (path difference)/λ = k 係同一樣野黎架，計到 k 係 integer (n) 就係 constructive，k 係一個 integer + 1/2 (n + 1/2) 就係 destructive [當然個 source 要 coherent]
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