The cubic kilometer is a metric unit of volume equal to 1,000,000,000 cubic meters. The symbol of the cubic kilometer is kmÂ³ . km3 = 1,000,000,000 m3 = 109 m3. To convert cubic kilometers to hmÂ³, damÂ³, mÂ³, dmÂ³, cmÂ³ and mmÂ³ , multiply by one followed by as many trios of zeros as there are places between the cubic kilometer and the other unit.
Rod photoreceptors are very sensitive to light and are responsible for night vision. These are the most abundant cell type in the human retina and are located closest to the back of the eye, near the retinal pigmented epithelium (RPE).
In cone cells, there are different types of opsins that combine with retinal to form pigments called photopsins. Three different classes of photopsins in the cones react to different ranges of light frequency, a differentiation that allows the visual system to calculate color.