code: def Fsphere(q, R):
      
      return 4 * np.pi / q ** 3 * (np.sin(q * R) - q * R * np.cos(q * R))
docs: Scattering form-factor amplitude of a sphere normalized to F(q=0)=V
  
      Inputs:
      -------
          ``q``: independent variable
          ``R``: sphere radius
  
      Formula:
      --------
          ``4*pi/q^3 * (sin(qR) - qR*cos(qR))``