What’s the difference between a polar and a nonpolar covalent bond

A covalent bond that has an unequal sharing of electrons, as in part (b) of Figure 4.4. 1, is called a polar covalent bond. A covalent bond that has an equal sharing of electrons (part (a) of Figure 4.4. 1) is called a nonpolar covalent bond.

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.