Question

Natasha holds the two ends of a string in her hands and then moves her hands up and down so that a wave travels from one end of the string to the other end. In which case will she have a standing wave along the string?

A. The resultant wave rises and falls in amplitude over time and has a frequency equal to that of the waves.

B. The resultant wave has a fixed amplitude and a frequency twice that of the waves.

C. The resultant wave has a fixed amplitude and a frequency equal to that of the waves.

D. The resultant wave rises and falls in amplitude over time and has a frequency twice that of the waves.

Answer 1

The awnser to this question is B

Answer 2

C. The resultant wave has a fixed amplitude and a frequency equal to that of the waves.

Step-by-step explanation:

When a wave superimpose with its own reflected wave then the resultant two waves will form a standing wave

so here let say the two waves are

`y_1 = Asin(\omega t - kx)`

`y_2 = A sin(\omega t + kx)`

now by superposition principle of above two waves

`y = y_1 + y_2`

`y = Asin(\omega_1t - kx) + A sin(\omega_2t + kx)`

`y = 2Acos(kx)sin(\omega t)`

so above is the resultant standing wave equation in which frequency will remain same and amplitude is fixed or constant