A wave disturbance in a medium is described by  y=0.02cos50πt+π/2cos10πx  where x, y are in meters and 't' in second.Which option is incorrect.

Comparing it with y=Acoswt+π/2coskx  If kx=π/2  , a node occurs  ∴ 10πx=π/2 ⇒x=0.05 m Hence, nodes will occur at 0.05 ,0.15, 0.25.....   If kx=π ,  an antinode occurs    ∴10πx=π ⇒x=0.1 m Hence, anti-nodes will occur at  0.1 , 0.2 , 0.3....  Also wave speed v=w/k=50π10π=5 m/sec  ∴λ=2π/k=2π/10π=0.2 m