Thursday, March 30, 2006

Mirage

Light refraction is a beautiful thing. It brings us lots of beautiful images and one of them is a mirage.

We might have heard of a mirage before but what is it actually and how does it look like? I have heard of it before and imagine that a mirage must be an amazing sight. Today, nothing to do, I did some research on Mirages.

Inverted Mirage of a boat

Most people's impression of mirages comes from comic books, for instance the elusive and distant mirage of an oasis which tends to appear to Donald Duck during adventures in the desert. People consequently tend to conclude that the mirage is a phenomenon produced by the delusions of a person who is exhausted by heat and thirst, a hallucination which exists only in the imagination of that person, rather than something which can be documented in, for instance, photographs.

On the other hand, most people are familiar with the shimmering pools of water that can often been seen on hot pavements on summer days. These apparent pools are not given any mystical connotations, however, even if they are in fact the same phenomenon as the mirage of an oasis in the desert: the sky and its blue colour appear to be reflected above a hot surface, producing an illusion of water, which constantly recedes out of reach before the approaching traveller.


The pool of water you see on the road is NOT a pool of water. It is just a mirage and when you approach it, the 'pool of water' will disappear.

There are 2 kinds of mirage. One is the inferior mirage which is like the photo shown above and the second is superior mirage. The superior mirage will have the mirage projected above the actual object instead of below it.


When we view an inferior-mirage "water pool" on a road or desert or other hot surface, what we are actually seeing is the image of the bluish sky being strongly refracted by the hot air near the surface so that it appears to our mind to be water lying on the surface. The appearance of the inferior mirage always indicates that the surface air is much warmer than the air above it due to the strong heating of the surface by the sun or some other heat source. This temperature structure -- very hot below and cool above -- causes light rays passing through it to be bent upward.


The superior mirage occurs under reverse atmospheric conditions from the inferior mirage. For it to be seen, the air close to the surface must be much colder than the air above it. This condition is common over snow, ice and cold water surfaces. When very cold air lies below warm air, light rays are bent downward toward the surface, thus tricking our eyes into thinking an object is located higher or is taller in appearance than it actually is.

I found some photos of Inferior Mirage. Interesting photos..


You can see a white light house but the white lighthouse is not there actually. It is an inferior mirage.


Mirage of the lighthouse and a boat. The boat seems to be floating on the horizon.

Images of Superior Mirage. Superior Mirage is more rare as there are alot of specific conditions required. A slight difference of height or angle will result in not seeing the mirage at all.


You see the small white house at the horizon? It is not a real house, just a mirage. There is no land there at all.


Another example of superior mirage.

I found a link to view a video of mirage taken in Finland. Click on the link below to view it.

http://virtual.finland.fi/stream/A_Ship_of_Many_Shapes.ram

Besides mirages, light refraction also creates other beautiful sight phenomenon.

Rainbows:


Double rainbows:

Halos:

Complex Halos:

There also lots of images of mirages during sunset and these the light refraction can cause the last rays of the sun to turn green.

... Tired liao.... Zzzzz..

5 comments:

Joucads said...

Wow, I am impress by your research siah.. Cool :)

Anonymous said...

very qim... thk u can do lighting for ang shwo.. heheh...xj

Miko said...

joucads: Thank you for your comment.. u rarely comment sia.~

XJ: erm, I think i cant design lightings leh.. why not let the white light shine on the stage thru out the whole show? hee hee

Kongming said...

reminded me of MGM Mirage...

melmeowz said...

HWWWAHHHHH~~ GEOGRAPHY LESSON LEH..