What does it mean when a wave's amplitude increases?

It becomes shorter

Explanation:

A wave, such as a Soundwave, controls volume based on it's Wavelength. A Louder sound has a shorter wavelength, a softer sound has it's waves spread out more. Amplitude is simply a fancy name for Volume in Amps. When amplitude increases, the volume increases. Thus, waves become shorter.

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.