# TPRH SW Chemistry, Passage 15

#### MelloTangelo

5+ Year Member
p. 291

I couldn't find a thread over this passage, so I decided to make one. I'm having a bit of trouble wrapping my head around it. I don't know how likely it is that I would get a graph like this on the real test, but I know I'm having a huge problem reading it. The passage says that if the blue cone is excited by 90%, and the green cone by 15%, we get the color blue. That seems to line up. Now, if the red cone is excited by 100%, and the green cone by 50%, the color is orange. How do you decide that? From what I can tell, the dotted line is between yellow and orange, so how do we know which one to choose? Is orange chosen because there's more red than green?

Question 5., because of this, was quite hard to completely understand. I couldn't figure out what constituted what color. The answer for question 6 also involved summing up parts of the graph, but I could not for the life of me figure out where they got these numbers from.

Maybe I'm missing something very obvious, but any help would be greatly appreciated!

Thanks!

#### DoctorInASaree

Green Yellow Orange Red
50% green 50% Red yields yellow
If Red > 50% then it will most likely yield orange (closer to red because more red is present).

Q5 - For the protanope (absence of red cone) purple and yellow can be detected, the trick here is that red will also be detected just as gray (not red). However, gray is still a color!

For the deuteranope (absence of green cone) yellow will appear to be red, and red will be appear to be red. Purple will be distinguished as purple. So, the observer, sees only purple and red - two colors. Therefore answer choice C of 3 for protanope and 2 for deuteranope is correct.

Q6 - I didn't even refer to the passage for this question, because I know, intuitively, that yellow is BRIIIIIIIIIIIIGHT .
Okay, perhaps you're a smarty-pants, and would like a better answer. Here's how I would approach it intuitively: yellow, blue, violet, or red? Violet and blue are dark. Red is pure, and yellow is a mixture of green and red. I mean think about it - why do we think that yellow is brighter than white? White is blue, red, and green; whereas yellow is not influenced by blue (which is darker).

OR you could add up the absorption numbers. Red is red, yellow is green + red, blue is green + blue, violet is violet. (TPR solution).

MelloTangelo
OP

#### MelloTangelo

5+ Year Member
Thank you, Dr. Saree!

By reading your response, I realized one grave mistake in my attempt to solve this passage. I was relying way too much on the graph, and way too little on my intuition! If i just thought about things in a way that was applicable to the real world, I'm sure I would have gotten a lot more questions right.

Let's hope I can stop that mistake from happening again!