For example, a telescope with a focal length of 2000mm has twice the power and half the field of view of a 1000mm telescope.

比如，与焦距为1000mm的望远镜相比，2000mm焦距望远镜的放大率和视场范围分别是前者的2倍和1/2。

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By assuming the weak lens focal length expression to be the first term in a power series a simple and accurate formula can be derived for the objective focal length of a magnetic electron lens.

用假设弱透镜焦距表达式是一个幂级数中的第一项的方法，可以导出相当准确且便于实用的电磁电子透镜物镜焦距公式。

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National focal points often have limited authority and very little access to a country's true power base.

国家归口单位的权限往往十分有限，极少可以接近国家的真正权力基础。

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The focal point of the controversy is the 1987 Constitution, drawn up after the People Power revolution ousted the dictatorship of Ferdinand Marcos the previous year.

CNN: The Battle Lines Form

We are finding a vision that is really bringing the power of all of our groups to bear, and Big Data is a focal point.

FORBES: Names to Know in Big Data: Hitachi Data Systems (HDS)

As for the liquid lens, Nippon Electric Glass' version uses low-power electric field to control its liquid crystal molecular orientation, thus changing the focal point.

ENGADGET: Nippon Electric Glass demos liquid crystal lens and 'invisible glass' at CEATEC (video)