Which of the following are the primary colours of light?
Blue, Red and Green
Identifying Primary Colours of Light
Understanding the primary colours of light is a fundamental concept in physics, specifically in the study of optics and colour theory. Primary colours are those that cannot be created by mixing other colours. Instead, they are the foundational colours used in an additive colour system, like the one governing how light mixes.
What are Primary Colours of Light?
In the context of light (also known as the additive colour system), the primary colours are the set of colours that, when mixed in varying proportions, can produce most other colours, including white light when mixed equally.
The primary colours of light are:
- Red
- Green
- Blue
This system is often referred to as the RGB colour model, widely used in displays like computer monitors, televisions, and phone screens. These devices create all the colours you see by varying the intensity of tiny red, green, and blue light emitters.
Mixing Primary Colours of Light
When primary colours of light are mixed, they produce secondary colours of light:
- Red + Green = Yellow
- Red + Blue = Magenta
- Green + Blue = Cyan
- Red + Green + Blue = White
Analyzing the Given Options
Let's look at the options provided and compare them to the known primary colours of light:
| Option | Proposed Colours | Match Primary Colours of Light? | Explanation |
|---|---|---|---|
| 1 | Yellow, Red and Green | No | Yellow is a secondary colour of light (made by mixing Red and Green). Red and Green are primary, but Yellow is not. |
| 2 | Blue, Red and Green | Yes | These are precisely the three primary colours in the additive colour system (light). |
| 3 | Violet, Red and Yellow | No | Violet and Yellow are not primary colours of light. Red is primary, but the set is incorrect. |
| 4 | Indigo, Violet and Green | No | Indigo and Violet are not primary colours of light. Green is primary, but the set is incorrect. |
Based on the analysis, the set of colours "Blue, Red and Green" correctly identifies the primary colours of light.
Revision Table: Primary Colours
| Type of Colours | Primary Colours | System |
|---|---|---|
| Light | Red, Green, Blue | Additive (mixing colours creates lighter results, adds up to white) |
| Pigment/Paint | Red, Yellow, Blue (traditional) OR Cyan, Magenta, Yellow (CMY/CMYK - more modern/accurate) | Subtractive (mixing colours absorbs more light, subtracts to black) |
Additional Information: Additive vs. Subtractive Colour
It's important not to confuse the primary colours of light with the primary colours of pigments (like paint or ink). They follow different systems:
- Additive Colour System (Light): This system starts with darkness and adds light. The primary colours are Red, Green, and Blue (RGB). Mixing them creates brighter colours, and mixing all three results in white light. This is how screens work.
- Subtractive Colour System (Pigment): This system starts with a surface that reflects light (like white paper) and adds pigments that absorb (subtract) certain colours of light. The traditional primary colours of pigment are Red, Yellow, and Blue. A more accurate set for modern printing is Cyan, Magenta, and Yellow (CMY), often with Black (K) added (CMYK). Mixing pigments absorbs more light, resulting in darker colours, and ideally mixing all three primaries results in black (or a dark brown in practice).
Since the question specifically asks about the primary colours of "light," we use the additive system.
Important Questions from Optics
Which one of the following colours may be obtained by combining green and red colours?
Directions: The following items consist of two statements, Statement I and Statement II. You are to examine these two statements carefully and select the answers to these items using the code given below:
Statement I: Diamond is very bright.
Statement II: Diamond has very low refractive index
A non-SI unit called 'nit' is the unit of which of the following photometric quantities used to measure a multitude of light intensity?
Which among the following is used as a reflector in search lights?
The incident ray, the ray perpendicular to the point of incidence, and the reflected ray all lie________.
