a)
Amplitude of wave is given as maximum displacement from mean position
So here amplitude is 1.25 cm
b)
Wavelength is the length of the wave that it travels in one time period
From graph we can say the wavelength is given as 3cm
PART C)
Time period of wave is the time after which it repeats its shape
Speed of the wave = 21 cm/s
time period = wavelength / speed
![T = (3)/(21)](https://img.qammunity.org/2019/formulas/physics/middle-school/exr539nidcbxp9sbeeormx33ip2osmr86e.png)
![T = (1)/(7) s](https://img.qammunity.org/2019/formulas/physics/middle-school/s6rx3n2lgeflf7h2tg7wkypsei9og5p5hb.png)
Now frequency is
![f = (1)/(T)](https://img.qammunity.org/2019/formulas/physics/middle-school/bt1be6wgsfnj3vuwxelozzckht4il3issj.png)
![f = 7 Hz](https://img.qammunity.org/2019/formulas/physics/middle-school/dguhq4yrekspnvgrjjoat5zhup8cdctli8.png)
PART D)
Time period = \frac{1}{f}[/tex]
![T = 0.143 s](https://img.qammunity.org/2019/formulas/physics/middle-school/5pbf41m89itmw683hd3j9kvqp9a0kd91cj.png)