Which equation should be used to calculate the speed of a wave?
speed = frequency x wavelength
speed = frequency x hertz
speed = period x wavelength
speed = period x hertz

Answer : The correct option is,

Speed = Frequency x Wavelength

Explanation :

Wave speed : It is defined as the speed at which a wave travels.

It is related to wavelength, frequency, and period.

The equations used are:

Speed = Frequency x Wavelength     ............(1)

As we know that,

So,

  .......(2)

The equation 1 and 2 are used to calculate the speed of wave.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.