f.3 physics (principal foci)

2011-12-17 10:27 pm

圖片參考:http://imgcld.yimg.com/8/n/HA08066696/o/701112170046013873412330.jpg

1. convex lens: where is principal foci?


圖片參考:http://imgcld.yimg.com/8/n/HA08066696/o/701112170046013873412341.jpg

2. concave lens: where is principal foci?
更新1:

感係咪姐話F'都可以叫principal focus?

更新2:

principal focus同focus有咩分別?

更新3:

thx very much

回答 (1)

2011-12-18 1:01 am
✔ 最佳答案
The principal foci have already been marked on the digrams. They are the points marked F and F'


2011-12-17 17:04:25 補充:
Please refer to the following web-page for explanation of the principal foci,

http://www.sasked.gov.sk.ca/docs/physics/u6b2phy.html

2011-12-18 01:51:55 補充:
Just read the para. extracted from the given web-page:

The principal focus (F) is a point on the principal axis where light comes to a focus (for a converging lens) or appears to be diverging from (for a diverging lens)...

2011-12-18 01:52:34 補充:
...Two foci exist, equidistant on either side of the lens, since light behaves the same way when travelling in either direction (Principle of Reversibility). The two foci, F and F' are called the primary principal focus and the secondary principal focus, respectively....

2011-12-18 01:52:48 補充:
... F, sometimes also referred to as the primary focal point, is shown on the right side of a converging lens, and on the left side of a diverging lens, while F', the secondary focal point is shown on the opposite side of each respective lens.)


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