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

  1. White and Red
  2. Red and Blue
  3. Black and White
  4. Black and Red

1 Answer

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Ans:- D

Explanation:- The color of an object is largely determined by its diffuse reflection coefficient(kd).

Kd is assigned a value between 0.0 and 1.0.

0.0 – for dull surface that absorbs almost all light

1.0 – for shiny surface that reflects almost all light.

You should understand the range of kd and its meaning very clearly. For colored surfaces, there are three kd values, one for red, green and blue. Let us consider a polygon with diffuse color(1,0,0). It reflects all of the red light it is hit with, and absorbs all of the blue and green(because red has a value 1, and green and blue has a 0).

If this red polygon is hit with a white light it will appear red. If it is hit with a blue light, or a green light, or an aqua light it will appear black(as those lights have no red component).

If it is hit with a yellow light or a purple light it will appear red(as the polygon will reflect the red component of the light). The kd value given in the equation is kd=(0.8,0.4,0)

What shall be the color of the object if the light used is blue and magenta?. That is the question.

Let us consider the first color. Blue light falls on the object. But the blue component of kd is 0. It means that color is going to be completely absorbed by the object and it will appear black. So, when blue light falls on the object, the object will appear black. Let us consider the next color. Magenta light falls on the object. Magents is a violet-red or purplish-red color. It is midway between red and blue. Since red has a high kd value, it will get reflected more and so the color of the object will be Red. So, the color of the object will be Black and Red. The correct option is D.
Answer:

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