弗蘭克赫茲實驗_論文講解

1、弗蘭克赫茲實驗 第一激發(fā)電勢的測定論文學校: 學院: 專業(yè)： 組員： 指導教師： 職稱：副教授 2012年7月 1日星期一摘要：本實驗通過改變燈絲電壓， 得觀察和理解分析， 得到氬原子的第一激發(fā)電勢 。關鍵詞：弗蘭克 赫茲 汞第一激發(fā)態(tài) 近代物理實驗（一） 引言 1913 年丹麥物理學家玻爾（NBohr）提出并建立了玻爾原子模型理論，認 為有原子能級存在。光譜學的研究證明了原子能級的存在，原子光譜中的每根譜線都相應表示了原子從某一較高能態(tài)向另一較低能態(tài)躍遷時的輻射。然而，原子能級的存在除了可由光譜研究推得外，1914 年德國物理學家夫蘭克和赫茲用慢電子與稀薄氣體原子碰撞的方法，使原子從低能級激

2、發(fā)到高能級。通過測量電子和原子碰撞時交換某一定值的能量，觀察測量到了汞的激發(fā)電位和電離電位，直接證明了原子內(nèi)部量子化能級的存在，也證明了原子發(fā)生躍遷時吸收和發(fā)射能量是完全正確的、不連續(xù)的，為早一年玻爾發(fā)表的原子結(jié)構理論的假說提供了有力的實驗證據(jù)。他們因此而分享了1925 年諾貝爾物理學獎。其實驗方法至今仍是探索原子結(jié)構的重要手段之一。玻爾因其原子模型理論獲 1922 年諾貝爾物理學獎，而夫蘭克與赫茲的實驗也于 1925年獲此大獎。夫蘭克-赫茲實驗與玻爾原子理論在物理學的發(fā)展史中起到了重要的作用。 （二） 實驗設備 （ 電腦XDFP軟件 F-H實驗管 WNZK-維度控制儀 FH-II弗蘭克赫茲試

3、驗儀 ）（三） 實驗原理夫蘭克-赫茲實驗的物理過程圖1 夫蘭克-赫茲實驗原理圖 圖中左側(cè)為夫蘭克-赫茲管（F-H管），它是一種密封的玻璃管，其中充有稀薄的原子量較大的汞或惰性氣體原子。在這里燈絲用來對陰極K加熱，使其發(fā)射熱 電子。燈絲電壓Ur越高，陰極K發(fā)射的電子流也就越大。第一柵極G1的主要作用是消除空間電荷對陰極電子發(fā)射的影響。柵極G1和陰極K之間的電壓通常只有幾伏。第二柵極G2的作用是在G2和K之間形成對電子加速的靜電場。由陰極K發(fā)射的絕大多數(shù)熱電子被柵極G1和G2所接收，并且其中被柵極G2接收的比例隨加速電壓UG2K的升高而增大。少量的發(fā)射電子穿過柵極G2達到極板P，形成板流IP。板流

4、IP的大小由微電流測試儀進行測量。在板極P和G2之間加有一反向拒斥電壓UG2P，它對電子減速，使經(jīng)過碰撞后動能非常低的電子折回并被柵極G2接受，從而起到調(diào)節(jié)板流IP大小的作用。 設汞原子的基態(tài)能量為E1，第一激發(fā)態(tài)能量為E2，且由熱陰極發(fā)射的電子初速度為零。受加速電場U2作用，電子到達柵極G2時所獲得的能量為E=eU2 ，具有這種能量的電子與汞原子發(fā)生碰撞。當U2較低時，電子能量eU2小于原子的激發(fā)能（即eU2eUG2P時，電子又能到達板極，使板流IP回升。當U2增大到2U0時，電子經(jīng)第一次非彈性碰撞后的剩余能量足以使其與汞原子產(chǎn)生第二次非彈性碰撞，汞原子再次從電子中取得能量，能量交換的結(jié)果使

5、IP再次下降。同理可知，U2繼續(xù)增大時，電子會在第二柵極G2附近與汞原子發(fā)生第三次、第四次、非彈性碰撞，引起板流IP的相應下跌?？梢?，隨著加速電壓U2的增加，板流IP會周期性地出現(xiàn)極大值和極小值，凡滿足加速電壓U2=nU0（n=1,2,3,）時，板流IP都會相應下跌，形成規(guī)則起伏的IP-U2特性曲線。曲線各峰值之間的等間隔規(guī)律表明：碰撞過程中電子有確定的能量傳遞給汞原子，而與相鄰的兩板流極大值（或極小值）所對應的加速電壓的差值就是汞原子的第一激發(fā)電位U0 。它的公認值為4.9V。 圖2 充汞F-H管的Ip-U2特性曲線 （四） 實驗數(shù)據(jù)處理 （一） 氬原子第一激發(fā)電勢的測定。 表一 實驗參數(shù)記

6、錄電流量程10uAVg1k1.1v燈絲電壓2.8vVg2k4.5v起始電壓0v測量步距0.1終止電壓100v溫度27.0等待時間0.4s 表二 氬原子第一激發(fā)電勢峰值峰谷數(shù)值記錄表峰值電壓 (/v)14.225.136.448.460.773.586.8峰谷電壓 (/v)19.030.442.154.366.879.8 根據(jù)公式： Vgk=nvg (n=1.2.3.4) 令Y=k*x+b (其中k=vg n=x)所以根據(jù)最小二乘法 利用EXCEL可以求得 根據(jù)表二中的數(shù)據(jù)（一） 利用其峰值計算第一激發(fā)電勢 k=12.105v r*r=0.997997 SA(x)=0.22v 所以： Vg=12

7、.11v r=0.998998 SA(Vg)=0.22v 所以： Vg=(12.11+-0.22) v根據(jù)表二中的數(shù)據(jù)（二） 利用其谷值計算第一激發(fā)電勢 k=12.161v r*r=0.999897 SA(x)=0.18v 所以： Vg=12.161v r=0.99995 SA(Vg)=0.18v 所以： Vg=(12.16+-0.18) v （三） 氬原子 IpVg2k的測定 表3. IpVg2k數(shù)據(jù)記錄表 004.4108.81213.2200.104.5108.91413.3210.204.61091313.4200.304.7109.11313.5200.404.8109.21213.

8、6210.504.9109.31313.7210.605109.41213.8200.705.1109.51313.9220.805.2109.612140.905.3109.71214.123105.4109.81414.2231.105.5109.91414.3221.205.610101314.4231.3105.71010.11214.5231.4105.81210.21314.6241.5105.91210.31314.7251.61061310.41214.8251.7106.11210.51314.9241.8106.21110.61315251.9106.31210.71315

9、.1262106.41210.81515.2262.1106.51210.91415.3252.2106.613111415.4262.3106.71111.11415.5272.4106.81211.21415.6262.5106.91211.31315.7262.61071.211.41415.8262.7107.11011.51415.9262.8107.21211.61516262.9107.31111.71416.1263107.41211.81516.2253.1107.51211.91516.3253.2107.6121716.4253.3107.71112.11516.5253

10、.4107.81212.21516.6253.5107.91212.31716.7243.61081112.41716.8253.7108.11312.51716.9243.8108.21112.61717233.9108.31212.71717.1234108.41212.81817.2224.1108.51312.91917.3224.2108.613131917.4224.3108.71313.11917.52217.621225726.46226.46217.72122.15826.56326.56317.82022.25626.66326.66317.92122.35326.7612

11、6.761182122.45226.76026.76018.12222.55326.95926.95918.22122.6552758275818.32222.75427.15827.15818.42222.85527.25727.25718.52322.95527.35527.35518.624235627.45327.45318.72423.15827.55227.55218.82623.25527.65027.65018.92623.35627.74727.747192723.45827.84727.84719.12823.55827.94427.94419.22923.65828422

12、84219.33023.75828.14128.14119.43123.85928.23928.23919.53323.96628.33628.33619.635246028.43628.43619.73724.15928.53328.53319.83824.26028.63328.63319.93924.36128.72928.729204224.46128.82428.82420.14324.55928.92428.92420.24424.6612922292220.34624.76129.12029.12020.44624.86129.21929.21920.54924.96129.31

13、829.31820.650256229.41829.41820.75125.16329.51729.51720.85225.26329.61729.61720.95425.36329.71729.717215525.46329.81629.81621.15525.56329.91829.91821.25525.6643018301821.35825.76330.12030.12021.45925.86330.22330.22321.56025.96430.32430.32421.661266330.42530.42521.75626.16330.52830.52821.85626.26230.

14、63030.63021.95526.36330.73230.73226.46235.210135.210135.210126.56335.310135.310135.310126.66335.410135.410135.410126.76135.510335.510335.510326.76035.610335.610335.610326.95935.710235.710235.7102275835.810235.810235.810227.15835.910235.910235.910227.25736103361033610327.35536.110436.110436.110427.45

15、336.210336.210336.210327.55236.310436.310436.310427.65036.410336.410336.410327.74736.510336.510336.510327.84736.610236.610236.610227.94436.710336.710336.7103284236.810336.810336.810328.14136.910236.910236.910228.23937102371023710228.33637.110137.110137.110128.43637.210037.210037.210028.53337.310037.

16、310037.310028.63337.410037.410037.410028.72937.59937.59937.59928.82437.69937.69937.69928.92437.79737.79737.797292237.89737.89737.89729.12037.99637.99637.99629.21938963896389629.31838.19438.19438.19429.41838.29138.29138.29129.51738.39238.39238.39229.61738.49038.49038.49029.71738.58838.58838.58829.816

17、38.68638.68638.68629.91838.78338.78338.783301838.88338.88338.88330.12038.97938.97938.97930.22339773977397730.32439.17439.17439.17430.42539.27039.27039.27030.52839.36939.36939.36930.63039.46639.46639.46630.73239.56439.56439.56448.412748.412748.412748.412748.512648.512648.512648.512648.612648.612648.6

18、12648.612648.712648.712648.712648.712648.812448.812448.812448.812448.912548.912548.912548.91254912549125491254912549.112249.112249.112249.112249.212249.212249.212249.212249.312249.312249.312249.312249.412149.412149.412149.412149.512049.512049.512049.512049.611849.611849.611849.611849.711849.711849.7

19、11849.711849.811649.811649.811649.811649.911449.911449.911449.91145011350113501135011350.111250.111250.111250.111250.211050.211050.211050.211050.310850.310850.310850.310850.410750.410750.410750.410750.510650.510650.510650.510650.610250.610250.610250.610250.710050.710050.710050.710050.89850.89850.898

20、50.89850.99750.99750.99750.997519551955195519551.19051.19051.19051.19051.28851.28851.28851.28851.38651.38651.38651.38651.48551.48551.48551.48551.58351.58351.58351.58351.67951.67951.67951.67951.77751.77751.77751.77751.87651.87651.87651.87651.97451.97451.97451.974527152715271527152.16952.16952.16952.1

21、6952.26852.26852.26852.26852.36752.36752.36752.36752.46552.46552.46552.46552.56452.56452.56452.56452.66452.66452.66452.66452.76252.76252.76252.76257.211761.6138669170.413757.312061.713766.19070.514057.412261.813766.29070.614157.512161.913666.39170.714157.61256213566.49270.814257.712562.113366.59370.

22、914557.812662.213266.6937114457.912862.313266.79471.11455812962.413066.89471.214658.113262.512866.99571.314858.213262.6129679671.414758.313462.712967.19671.514958.413362.812767.29671.615058.513562.912667.39871.715058.61366312467.49971.815258.713663.111767.59971.915258.813763.211467.61017215258.91396

23、3.311167.710372.11555913963.410967.810372.215459.114063.510867.910372.315459.213863.61076810572.415559.314163.710468.110872.515659.414263.810468.210972.615659.514263.910368.311072.715559.61436410168.411172.815559.714364.19968.511372.915759.814364.29968.61147315759.914464.39868.711673.11566014364.497

24、68.811773.215660.114564.59568.911973.315760.214564.6956912073.415660.314464.79469.112173.515560.414464.89369.212273.615660.514464.99269.312573.715560.6144659269.412573.815560.714465.19169.512673.915660.814365.29169.61297415360.914365.39069.712974.11536114365.49169.813274.215261.114265.59069.913274.3

25、15261.214165.6907013474.415161.314065.78970.113574.515061.414165.89170.213474.615161.513965.99170.313774.714874.814779.212683.61628817374.914779.312683.716388.11747514679.412683.816588.217275.114779.512783.916588.317275.214579.61268416688.417175.314479.712784.116788.517175.414479.812884.216888.61717

26、5.514279.912884.316988.717075.61418013084.417088.816975.714180.113084.517188.917175.813980.213084.61728917075.913980.313184.717189.11697613880.413284.817289.216776.113880.513384.917189.316976.213680.61338517389.416976.313680.713585.117389.516776.413580.813585.217389.616876.513480.913785.317489.71677

27、6.61328113785.417589.816776.713281.113685.517589.916776.813181.213885.61759016576.913181.313985.717590.11667712981.414085.817590.216577.112881.514185.917690.316577.212881.61418617790.416577.312881.714286.117590.516477.412781.814486.217590.616577.512781.914586.317790.716577.61268214686.417790.816477.

28、712682.114786.517590.916477.812582.214986.61769116377.912682.314986.717591.11647812582.415086.817791.216278.112582.515286.917791.316278.212582.61538717691.416478.312582.715487.117491.516378.412582.815487.217491.616378.512582.915587.317591.716278.61248315787.417591.816478.712583.115787.517391.916478.812583.215887.