Question

If an earthquake wave having a wavelength of 13 km caused the ground to vibrate 10 times each minute, what is the speed of the wave?

1.2 km/s
2.2 km/s
220 m/s
22 m/s

If the amplitude in a sound wave is doubled, by what factor does the intensity of the wave increase?
2
1
8
4(my choice)

Answer 1

#1

Wavelength = 13 km

it vibrates 10 times each minute

so the frequency is defined by the number of vibrations per second

`f = 10 per\: min`

`f = (10)/(60)`

now the speed of wave is defined as

`v = \lambda* f`

`v = 13* (1)/(6) = 2.2 km/s`

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

`Intensity = k*(amplitude)^2`

k = constant

so if amplitude is doubled then its intensity will be increased by its square

so intensity is 4 times