The equation of a plane progressive wave is given by $y = 0.6 \sin 2\pi \left( t - \frac{x}{2} \right)$. On reflection from a denser medium,its amplitude becomes $2/3$ of the amplitude of the incident wave. The equation of the reflected wave is:

• A
  $y = 0.6 \sin 2\pi \left( t + \frac{x}{2} \right)$
• B
  $y = -0.4 \sin 2\pi \left( t + \frac{x}{2} \right)$
• C
  $y = 0.4 \sin 2\pi \left( t + \frac{x}{2} \right)$
• D
  $y = -0.4 \sin 2\pi \left( t - \frac{x}{2} \right)$