Questions

The trichromatic coordinates are defined by:

or

From table I, we have:

or

which leads to:

The trichromatic coordinates indicate that the stimulus is close to the equienergetic white, whose coordinates are .

For a pure (monochromatic) color, the trichromatic coordinates are given by :

hence: , ,

For an additive mixture of two colors and whose trichromatic coordinates are and respectively, the components of the resulting stimulus are :

Since the trichromatic coordinates are :

for stimulus and

for stimulis

Then for stimulus we have

With

which leads to:

or

And, by definition :

From the expressions derived in question 6, we may write:

Besides we know that:

(from question 3 ) and

( from question 5 )

then we can finally write:

From table 1, the trichromatic coordinates of the A, C and D65 illuminants are :

In the plane the distances , and are :

Then ; ;

Therefore, the stimulus whose trichromatic coordinates are:

is closer to the A illuminant.

The purity is defined by :

With the equienergetic stimulus defined by its coordinates equal to :

and

In this case,

so:

Here  and so that

We may also calculate the purity p by considering that with and then

with  et .

this lead to  .