In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions.
Answer:
A) That man-made trade barriers are the biggest challenge facing Africa's international trade success.
Explanation:
Based on the discussion of high trade costs, the presence of numerous tariffs, and problems with customs procedures and duties it is clear that the author feels that man-made trade barriers are the biggest challenge facing Africa's international trade success.
If the two cups are the same/equal in all regards the spoon makes the difference in heat loss. Metal spoon is a good conductor, heat conducts up the spoon handle. Radiant and convection losses occur in the surrounding air. Metal becomes a “heat sink”.
Spoon will feel warmer to the touch than a pottery or foam cup that is not a good conductor.
Solids, liquids and gases :
In solids the particles like molecules of the substance - are very close to each other. They cannot move far from their positions. In liquids they are separated by some more distance. SO molecules are freely moving inside liquid. But in gases the molecules are free to move with in the volume.
Gaseous molecules have higher speeds.
Solids have good conductivity of electricity. Some liquids are also conductive. gases may be less conductive.
Gases have no shape of their own. Liquids do not have a shape too. Solids can have some shape and retain their shape.
Gases and Liquids flow. Solids do not flow.
Many gases may be invisible or may be faint in color. Visibility of liquids and solids is high.
Gases may not taste. they may smell. Solids and liquids may taste and may or may not smell.
Solids may be transparent to light or may be opaque. Gases may be highly transparent to light.
Sound travels in solids faster than in gases.
As heat enters the surface of the Earth the gas traps it and is not radiated it's absorbed.
