The wavefronts of a light wave travelling in vacuum are defined by x + y + z = c . The angle formed by the direction of propagation of the light with the X-axis is

Step-by-step solution

The equation of the wavefront is given by x + y + z = c . The direction of propagation of a light wave is always perpendicular to its wavefront. The normal vector to the plane x + y + z = c represents the direction of propagation, which is n = i + j + k . The angle made by the direction of propagation with the X-axis (direction vector i ) is given by = n i | n | | i | = ( i + j + k ) i 1^2 + 1^2 + 1^2 1^2 = 1 3 = ⁻¹ ( 1 3 )