雙重彩虹並非像歲月神偷所說的罕見, 才會被神秘客拍到...
亞歷山大帶
亞歷山大帶或亞歷山大暗帶是與彩虹結合在一起的光學現象, 因為亞歷山大(Alexander of Aphrodisias)在西元200年最先描述, 因而以他為名. 由於角度上的偏折, 它出現在虹與霓中間的空隙. 這兩道弧是因為光學上的最小偏向角才會存在的, 偏離度比最小偏向角小的光線永遠不會抵達觀測者的眼中.
虹的最小偏向角是137.5°, 光線的偏離可以達到180°, 導致光線反射至觀測者, 偏離了中間角度的光線照亮了彩虹的內側.
霓的最小偏向角大約是230°. 事實上, 這個角度大於180°, 造成霓的內外與虹相反, 因此它的顏色是反轉的，偏離角度較大的光線照亮了外弧的天空.
在這兩道弧的中間是天空未被照亮的亞歷山大帶, 儘管它可能有助於其他地區的觀測者看見彩虹, 被雨滴反射的陽光反應在天空中這一區域的光線不能到達觀測者的眼中.
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雙重彩虹
外圈為霓，內圈為虹
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| 攝於2012年6月19日. 香港. |
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| 坐巴士時用質素差的手機拍的... |
拍了很多張照片, 但就這幾張比較滿意
Rainbow Connection
A very classic song from the muppets.
Why are there so many
Songs about rainbowsAnd what's on the other side
Rainbow's are visions
They're only illusions
And rainbows have nothing to hide
So we've been told and some chose to
Believe it
But I know they're wrong wait and see
Someday we'll find it
The Rainbow Connection
The lovers, the dreamers and me
Who said that every wish
Would be heard and answered
When wished on the morning star
Someone thought of that
And someone believed it
And look what it's done so far
What's so amazing
That keeps us star gazing
What so we think we might see
Someday we'll find it
That Rainbow Connection
The lovers the dreamers and me
All of us under its spell
We know that it's probably magic
Have you been half asleep
And have you heard voices
I've heard them calling my name
Are these the sweet sounds that called
The young sailors
I think they're one and the same
I've heard it too many times to ignore it
There's something that I'm supposed to be
Someday we'll find it
The Rainbow Connection
The lovers, the dreamers and me
(Something, somewhere, I konw we'll find it)
The lovers, the dreamers and me
