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With γ-rays of various wave-lengths the number of counts produced in a Geiger-Muller counter of Pb-wall was determined in equal time intervals. The same experiment was carried out with a counter of Al-wall. Let Npb and NA1 represent the number of counts produced in the Pb-counter and Al-counter respectively by a beam of γ-rays of even wave-length in a given time interval. The ratio Nph/NA1 observed decreases at first with the wavelength of the incident beam due to the diminishing photo-electric of lead. It is,... With γ-rays of various wave-lengths the number of counts produced in a Geiger-Muller counter of Pb-wall was determined in equal time intervals. The same experiment was carried out with a counter of Al-wall. Let Npb and NA1 represent the number of counts produced in the Pb-counter and Al-counter respectively by a beam of γ-rays of even wave-length in a given time interval. The ratio Nph/NA1 observed decreases at first with the wavelength of the incident beam due to the diminishing photo-electric of lead. It is, however, found to increase by 16% when the wavelength of the incident radiation is decreased from a value 6.6 x. u. 4.7 x. u. This rising is due to particles produced by the interaction of hard γ-rays with the Pb-nuclei. 能力极大的丙种镭辐射,可以影响原子核,这是新近发见的事实。为进一步的研究,我们把极硬的丙种镭辐射,照在铅的数电子管(Electron Counter)上结果:除了射出的光电子和反跳子(Compton RecoilElectron)外,还观察到一种电子(有阴阳二种),约占总数的百分之十七。这种电子的来源,现在有两种解释:1从原子核里射出。(2)直接由丙种镭辐射变成。 The effect of pressure on photographic sensitivity is discussed on the experimental basis that the quantity E/EC, where E is the illumination actually used when the photographic emulsion is under pressure, and Ee the illumination which would be required to produce the same optical density when the emulsion is under no pressure, is a function of pressure only and that for pressures greater than a certain value, E/Ee becomes a linear function of the pressure. 当照相时,照相片子——映像纸,软片,或玻璃板——被压,则其感光性减弱,是为照相的压力效应。设E为照相片子在压力P下得光密度d所需之光照度,若片子不受压力则用光照度E_e即可得此同一之光密度d,故E_e可称在压力P下E之有效照度。吾人实验证明E/E_e为压力P之函数,当p>200kg/cm~2时,E/E_e与P成正比例。 此照相的压力效应,与照相时所用光之颜色,极有关系。黄色光较绿色光为显,绿色光较蓝色光紫色光为显至紫外光则几无此效应。 又此效应之大小,随各种照相片子而不同。就我们所研究的蔡爱斯伊康正色软片,伊司门人像软片,和矮克发等色软片而论,以第一种为最大第二种次之第三种为最小。 这个效应,在实际上,或可有些应用。 Self-recording system is devised and used to measure potential gradient at Yenching. In fine weather the results show two maxima and two minima for a whole day. During raining potential gradient is constant at zero value, except when lightening and thunderstorm occur in which case the potential gradient changes rapidly both in magnitude and direction. 本篇所述,为在北平燕京大学用静电计及一连续记录器测量大气电位梯度之方法及结果测量方法,乃用一种均位器(eqalizer)将离地面约3至6米高之电位显示于静电计上再用照相纸将此电位制成连续记录。测量所得结果如下:晴天之电位梯度。一日之中,有二最高值及二最低值雨时梯度即降至零,且此值非至雨止不变。当闪电及雷飓时,梯度之方向与值,变易极速。且较晴天时为大。
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