Q47,paper 3, J12.The colour of an object is largely determined by its diffuse reflection coefficient. If Kd= (0.8, 0.4, 0), then what shall be the colour of the object, if the light used is blue and magenta ?

(A) White and Red
(B) Red and Blue
(C) Black and White
(D) Black and Red
Answer(d) Black and red.
The greater the angle between the normal and the vector from the point to the light source, the less light is reflected. Most light is reflected when the angle is 0 degrees, none is reflected at 90 degrees. In the above example: The amount of light seen by the viewer is proportional to the cosine of the angle between the normal to the polygon and the angle of incidence of the light ray. The diffuse illumination equation is: Intensity = Diffuse term I = Ip x Kd x cos(theta) Ip is the point light source's intensity Kd is the material's diffuse reflection coefficient and is a constant between 0 and 1 which varies from material to material. cos(theta) must be between 0 degrees and 90 degrees if the light is to have any effect on the polygon. Hence in our case Let angle is 0 and blue is only reflected half so option (A and C) fails because white is mixture of all colors and we know that according diffusion coeff (RBG) green is not reflected. Blue is reflected less than half so it cannot be blue.so B also fails and we have option D only.