21.
(2023·惠州模拟)
质谱仪被应用于分离同位素,图(a)是其简化模型。大量质量
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3Em%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1.60%3C%2Fmn%3E%3Cmo%3E%C3%97%3C%2Fmo%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E10%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmn%3E27%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsup%3E%3Cmtext%3Ekg%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
、电荷量为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3Eq%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1.60%3C%2Fmn%3E%3Cmo%3E%C3%97%3C%2Fmo%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E10%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmn%3E19%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsup%3E%3Cmtext%3EC%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
的质子,从粒子源A下方以近似速度为0飘入电势差为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3EU%3C%2Fmi%3E%3Cmn%3E0%3C%2Fmn%3E%3C%2Fmsub%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E450%3C%2Fmn%3E%3Cmtext%3EV%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
的加速电场中,从中央位置进入平行板电容器。当平行板电容器不加电压时,粒子将沿图中虚线从O点进入磁感应强度
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3EB%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E0.1%3C%2Fmn%3E%3Cmtext%3ET%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
的匀强磁场中,经磁场偏转后打在水平放置的屏上,已知磁场方向垂直纸面向外,电容器极板长度
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3EL%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E6%3C%2Fmn%3E%3Cmtext%3Ecm%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
, 两极板间宽度
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3Ed%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E2%3C%2Fmn%3E%3Cmtext%3Ecm%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
。现给平行板电容器加上图(b)所示的偏转电压,质子在电容器中运动的时间远小于电压变化的周期
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3ET%3C%2Fmi%3E%3C%2Fmath%3E)
, 水平屏分布在电容器竖直极板两侧,忽略粒子所受重力和粒子间的相互作用力,求:
![](//tikupic.21cnjy.com/2023/02/16/5c/7b/5c7b111ff053e619692190e5e9cde1da_392x212.png)