When blue light and green light are mixed, which colour of light is formed in the visible spectrum?

Introduction / Context:

This question tests basic knowledge of colour mixing in the context of light, not pigments. Understanding additive colour mixing is important in physics, computer graphics and display technology. When different primary colours of light are combined, they produce secondary colours. The question specifically asks what colour results from mixing blue and green light.

Given Data / Assumptions:

• The context is mixing coloured light, as in the RGB (red, green, blue) model used in screens and optics.
• Blue and green are both primary colours in the RGB additive system.
• We are asked about the resulting perceived colour when these two light colours overlap.
• Subtractive mixing of paints or pigments is not considered here.

Concept / Approach:

In additive colour mixing, the primary colours are red, green and blue. When two primary colours are added together, they form a secondary colour. Red plus green gives yellow, red plus blue yields magenta and green plus blue produces cyan. This is the basis for how television screens, computer monitors and projectors create a wide range of colours by combining different intensities of red, green and blue light.

Step-by-Step Solution:

Verification / Alternative check:

If you look at an image editor or graphics software that uses an RGB colour picker, you can simulate the combination by setting red intensity to zero and turning on equal amounts of green and blue. The resulting displayed colour is cyan, often used for backgrounds and design elements. This visual confirmation aligns with the theoretical additive colour model, verifying that cyan is the correct result.

Why Other Options Are Wrong:

Brown is typically a subtractive colour resulting from mixing paints or pigments and does not arise from simply mixing pure blue and green light. Black corresponds to the absence of light in additive mixing, which would occur only if no colour channels are active, not when two channels are combined. Violet arises when blue light is mixed with red light or when spectral components shift, not with green. Yellow is produced by mixing red and green light, not blue and green. None of these alternatives correctly match the additive mixing rule for blue and green.

Common Pitfalls:

Students sometimes confuse additive colour mixing (light) with subtractive colour mixing (paints or inks), where combining multiple colours can lead to darker shades like brown or black. Another pitfall is misremembering which pairs of RGB colours form which secondary colours. A simple memory aid is that the initials C, M and Y stand for cyan, magenta and yellow, which are produced by mixing pairs of RGB primaries: G plus B for cyan, R plus B for magenta and R plus G for yellow.

Final Answer:

When blue light and green light are mixed, the resulting colour is Cyan.