Senin, 30 Maret 2009
danau singkarak
Danau Singkarak berada di dua kabupaten di Sumatera Barat, Kabupaten Solok dan Kabupaten Tanah Datar. Dengan luas 107,8 km² danau ini merupakan danau terluas ke-2 di Pulau Sumatera. Danau ini merupakan hulu Batang Ombilin. Air danau ini sebagian dialirkan melewati terowongan menembus Bukit Barisan ke Batang Anai untuk menggerakkan generator PLTA Singkarak di dekat Lubuk Alung, Padang Pariaman.
Selasa, 10 Maret 2009
Bunga Abadi
Bunga eidelweis sering juga disebut bunga abadi karena setelah dipetik eidelweis tidak layu.
Eidelweis merupakan tumbuhan pelopor bagi tanah vulkanik muda di hutan pegunungan dan mampu mempertahankan kelangsungan hidupnya di atas tanah yang tandus, karena mampu membentuk mikoriza dengan jamur tanah tertentu yang secara efektif memperluas kawasan yang dijangkau oleh akar-akarnya dan meningkatkan efisiensi dalam mencari zat hara. Bunga-bunganya sangat disukai oleh serangga, lebih dari 300 jenis serangga seperti kutu, tirip, kupu-kupu, lalat, tabuhan dan lebah terlihat mengunjunginya. Jika tumbuhan ini cabang-cabangnya dibiarkan tumbuh cukup kokoh, edelweis dapat menjadi tempat bersarang bagi burung tiung batu licik
Ranu Kumbolo
Selasa, 03 Maret 2009
Rainbows are an impressive natural spectacle since living memory. Among the first descriptions of rainbows there are those in the Bible (Genesis 9:13). The rescued on Noah's ark watched the first rainbow in the end of the Flood.
One can see this optical rainbow when sunshine and rain come together. The rainbow forms a circular ring with an angle of 42° relative to the observation direction around a virtual center exactly opposite to the sun. All spectral colors appear in narrow bands of intensified light with the colors from red to violet from the outside to inside. Under favorable conditions one can observe a second rainbow at a larger aperture angle of 51°, which is much paler and has the colors in a reversed order. Between the two rainbows there is a darker region, which is called "Alexander's dark band" (see Figure).
One can see this optical rainbow when sunshine and rain come together. The rainbow forms a circular ring with an angle of 42° relative to the observation direction around a virtual center exactly opposite to the sun. All spectral colors appear in narrow bands of intensified light with the colors from red to violet from the outside to inside. Under favorable conditions one can observe a second rainbow at a larger aperture angle of 51°, which is much paler and has the colors in a reversed order. Between the two rainbows there is a darker region, which is called "Alexander's dark band" (see Figure).
From the point of view of physics a rainbow appears when sunlight is refracted and bundled, which leads to the raise of light intensity in a narrow angular range. Looking microscopically we see the light of the sun falling onto many small raindrops. The light is at first refracted by entering the interior of the drops, then reflected at the back wall and finally refracted once again by exiting the drop. The total refraction angle is about 138° and this is at 42° with respect to the center of the rainbow. The different colors of light correspond to different wavelengths of light, which are refracted at slightly different angles, like by a prism, thus splitting the white sunlight into colors (dispersion).
The primary (main) rainbow is caused by refraction and reflection inside a raindrop. The secondary rainbow arises from a second total reflection, which reverses the order of colors and lets them appear paler.
The secondary rainbow is created by those light beams, which are reflected twice inside the raindrop. Therefore it is less intense and the order of colors is reversed. The dark band between the two rainbows is just a result of a redistribution of sunlight, which is focused into the rainbow angles. In physics there is no magic: If light gets brighter in one or two zones, this can happen only at the cost of another zone becoming darker.
So we can summarize that the rainbow is an optical phenomenon, which can be explained only by the wave nature of light.
So we can summarize that the rainbow is an optical phenomenon, which can be explained only by the wave nature of light.
Langganan:
Postingan (Atom)