F7 al phy...wave concept help

Question

1.激光系進行楊氏雙縫實驗時不能產生干涉條紋？Solution：激光單頻，非連續光譜，不產生最少強度。 （why）

2.楊氏雙縫實驗中，將兩縫的寬度收窄（並非兩縫的距離），會令到光強度下降及看到更多條紋？
有無數學方法可以證明？

3.有無一D既定的方法去判斷實物和虛物？

THANK YOU VERY MUCH!!!!

天同 · Accepted Answer

1. No, it is not true. A condition for interference pattern to be formed in the "double slit experiment" is the wave must be monochromatic (i.e. of single frequency).  A laser gives monochromatic light wave, thus can be used in "double slit" experiment to produce interference fringes.

2. You may refer to the animation given below:

http://lectureonline.cl.msu.edu/~mmp/kap27/Gary-TwoSlit/app.htm

3. Do you referto "real" and "virtual" images ?
"Real" images are those that are really exist and hence can be seen on a screen. "Virtual" image can only be perceived by the eyes and thus cannot be formed on a screen.

2011-10-25 11:53:13 補充：
Q2: the equation for light intensity in the double slit experiment is given in the following web-page:
http://vnatsci.ltu.edu/s_schneider/physlets/main/doubleslitintensity.shtml

2011-10-25 12:01:33 補充：
When a (the slit width) gets smaller, this sine function in the equation modulates the intensity and makes it lowered. Because the sine function also accounts for the diffraction effect, a narrow slit gives a more pronounced diffraction, hence more fringes appears.

F7 al phy...wave concept help

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