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標題: [問題] F.3 Physics Uniform Quiz Questions [打印本頁]

作者: Hin2000    時間: 2015-6-5 03:44 PM     標題: F.3 Physics Uniform Quiz Questions

(How to calculate?)


A diver is directly under a large patch of dirty oil floating on the water surface. The oil blocks all the light falling on it. Assume the oil patch is circular in shape and has a radius of 0.8 m. Find the minimum depth of the diver so that he can see objects above the water surface.
(Given: the refractive index of water = 1.33)

A. 0.7 m
B. 0.9 m
C. 1.1 m
D. 1.4 m

作者: Hin2000    時間: 2015-6-5 07:51 PM     標題: Phy Question

(How to calculate?)


A diver is directly under a large patch of dirty oil floating on the water surface. The oil blocks all the light falling on it. Assume the oil patch is circular in shape and has a radius of 0.8 m. Find the minimum depth of the diver so that he can see objects above the water surface.
(Given: the refractive index of water = 1.33)

A. 0.7 m
B. 0.9 m
C. 1.1 m

作者: aaalviny    時間: 2015-6-5 09:15 PM

雖然唔肯定你唔明邊一part, 但我嘗試逐part講:

思考模式: 題目要計depth, 畫圖會好睇d

part 1: 你能唔能夠畫到幅圖出黎? 如下

part 2: 佢潛得唔夠深的話, total internal reflection會令到冇光能夠由水上refract到身處海底既diver
佢越潛越深的話, 就越會望到多水面上既野 (黑 -> 紅 -> 綠)
(能理解 i 與 r 與 total internal reflection之間既關係?)

part 3: critical point如紅筆所示
sin theta = 1/1.33 by Snell's Law

part 4: 計min depth
tan theta = 0.8 / min depth
min depth = 0.7m


作者: andylai    時間: 2015-6-6 12:06 AM

引用:
原帖由 Hin2000 於 2015-6-5 03:44 PM 發表
(How to calculate?)


A diver is directly under a large patch of dirty oil floating on the water surface. The oil blocks all the light falling on it. Assume the oil patch is circular in shape and h ...


1. Total Internal Reflection!


2. Draw a right-angled triangle as shown in the figure


3. By General Snell's Law: (1.33) sinC = (1) sin(90) => C = 48.75


4. Tan(48.75) = 0.8 / d => d = 0.7 m


Do you understand why I have to draw the diagram as shown and do in this way?
作者: Hin2000    時間: 2015-6-6 12:45 PM

thx  
作者: TigerHix    時間: 2015-6-9 02:40 PM

我見到上面有人賣廣告呀~




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