问题 不定项选择

如图质子()、氘核()和α粒子()都沿平行板电容器两板中线OO'方向垂直于电场线射入板间的匀强电场,射出后都打在同一个与OO'垂直的荧光屏上,使荧光屏上出现亮点。则

[ ]

A.若它们射入电场时的速度相等,在荧光屏上将出现3个亮点

B.若它们射入电场时的动量相等,在荧光屏上将只出现2个亮点

C.若它们射入电场时的动能相等,在荧光屏上将只出现1个亮点

D.若它们是由同一个电场从静止加速后射入此偏转电场的,在荧光屏上将只出现1个亮点

答案

答案:D

单项选择题
单项选择题

(二)

Want a glance of the future of health care Take a look at the way the various networks of people about patient care are being connected to one another, and how this new connectivity is being exploited to deliver medicine to the patient—no matter where he or she may be.

Online doctors offering advice based on normal symptoms are the most obvious example. Increasingly, however, remote diagnosis will be based on real physiological data from the actual patient. A group from the University of Kentucky has shown that by using personal data assistance plus a mobile phone, it is perfectly practical to send a patient’s important signs over the telephone. With this kind of equipment, the cry asking whether there was a doctor in the house could well be a thing of the past.

Other medical technology groups are working on applying telemedicine to rural(countryside) care. And at least one team wants to use telemedicine as a tool for disaster need—especially after earthquakes. On the whole, the trend is towards providing global access to medical data and experts’ opinions.

But there is one problem. Bandwidth is the limiting factor for sending complex medical pictures around the world—CT photos being one of the biggest bandwidth users. Communication satellites may be able to deal with the short-term needs during disasters such as earthquakes or wars. But medicine is looking towards both the second-generation Internet and third-generation mobile phones for the future of remote medical service.

Doctors have met to discuss computer-based tools for medical diagnosis, training and telemedicine. With the falling price of broadband communications, the new technologies should start a new time when telemedicine and the sharing of medical information, experts’ opinions and diagnosis are common.

The "problem" in the fourth paragraph refers to the fact that ().

A.bandwidth isn’t big enough to send complex medical pictures

B.the second-generation of Internet has not become popular yet

C.communication satellites can only deal with short-term needs

D.there is not enough equipment for spreading the medical care