def getWave(Parms):
    """returns wavelength from Instrument parameters dictionary
    
    :param dict Parms: Instrument parameters;
        must contain:
        Lam: single wavelength
        or
        Lam1: Ka1 radiation wavelength
    
    :returns: float wave: wavelength
    
    """
    try:
        return Parms['Lam'][1]
    except KeyError:
        return Parms['Lam1'][1]
