Question

The word PHYSICS is written in red ink and the word CHEMISTRY is written in blue ink on a white piece of paper. They are viewed in red light. Which word will you be able to read? Why?

Answer 1

Hint: The visible spectrum of light ranging from 400 nm to 800 nm of wavelengths consists of 7 colors. All of them move at the same speed. Its combination is perceived as a white color in our brain. The colors that we see are the reflection of the colored wavelength that bounces off an object.

Complete step by step solution:
The spectrum of white light consists of 7 distinct colors: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. When white light hits an object that is colored, the object absorbs all the radiation except the color and reflects one color of wavelength, which our eyes perceive accordingly.
For example, if the light is incident on an object that is in green color, the object absorbs all the radiation except green and it reflects the green radiation, and hence, our eyes perceive the object as green color.
This proves that white light is essential for the colors to appear on the objects.
As per the question, we have two scenarios here:
If we view the first paper that has PHYSICS written in red ink under red light, it will be impossible to see the words. This is because the red color paint will camouflage with the background as the red light will turn the entire paper into a red color.
If we view the second paper that has CHEMISTRY written in blue ink under red light, the words will be visible because the blue color paint will standoff against the red background of the paper.

$\therefore$ If we view the second paper that has CHEMISTRY written in blue ink under red light, the words will be visible because the blue color paint will standoff against the red background of the paper.

Note:
Even though there are 7 distinct colors in the spectrum, they are classified into two major regions denoting the shade of the light: Red spectrum and the Blue spectrum. Objects that absorb the red spectrum appear blue and those that absorb the blue spectrum appear red.