Suppose you electrically charge a comb by running it through your hair and then shake it back and forth at a frequency of $2$ Hz$.$ This will produce a sound wave having a wavelength of $300000$ km and a speed of $300000$km $/$ s a sound wave having a frequency of $2$ Hz and a speed of $300000$km $/$ s a vibrating string having a frequency of $2$ Hz an electromagnetic wave having a frequency of $2$ Hz and a speed of $300000$km $/$ s