#1
Wavelength = 13 km
it vibrates 10 times each minute
so the frequency is defined by the number of vibrations per second
[tex]f = 10 per\: min[/tex]
[tex]f = \frac{10}{60}[/tex]
now the speed of wave is defined as
[tex]v = \lambda* f[/tex]
[tex]v = 13* \frac{1}{6} = 2.2 km/s[/tex]
so here velocity of wave is 2.2 km/s
#2
Intensity of wave is directly proportional to the square of its amplitude
so we can say
[tex]Intensity = k*(amplitude)^2[/tex]
k = constant
so if amplitude is doubled then its intensity will be increased by its square
so intensity is 4 times
