  A convex triangular obstacle forms a vital part of a periodic echellete
grating. A triangular grating is characterized by three parameters like period,
depth and flare angle. Knowledge of groove field is essential for precise
designing of triangular corrugated structures for studying the blazing effect
of propagating EM wave. In the present paper, an attempt has been made to
determine the power of Groove fields belonging to a pair of groove regions
adjacent to a convex triangular prism. Groove fields and their associated
powers based on Dirichlet conditions on the groove surfaces have been
determined. The governing Helmholtz wave equation has been solved for
determining the free surface field and the groove field. Fourier-Bessel series,
oblique coordinate transformations and Lommel's integral are used as tools.
