Hi there!
The Amplitude is the 'A' value of the following SHM equation:
[tex]x(t) = Asin(\omega t)[/tex]
Thus, the amplitude of this object:
A = 0.50 m
The period of vibration is equivalent to:
[tex]T = \frac{2\pi}{\omega}[/tex]
In this instance:
[tex]\omega = \frac{\pi}{2}[/tex]
Therefore:
[tex]T = \frac{2\pi}{\frac{\pi}{2}} = \frac{4\pi}{\pi} = \boxed{\text{ 4 seconds.}}[/tex]