Introduction to White Colour
We can call white light colourless daylight. Colour white contains all types of wavelengths of the visible spectrum. Each wavelength has an equal spectrum. Visible or white light comes before the infrared rays.
All the electromagnetic radiation that appears white to our eyes is called pure white light. Also, the sun emits visible light in which pure white colour exists. If you try to summon the entire emission power spectrum, you will find that the sun emits a little more infrared rays rather than visible light.
In this article, we will know the behaviour of white light and many related terms associated with it.
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White Meaning
White light or visible light is the portion of the electromagnetic spectrum. Our eyes can detect those lights with ease. Electrons inside the atoms and molecules of the visible light and it’s instantaneous near-infrared light help to absorb and emit the electromagnetic waves.
Frequencies of the Color White are in the visible range. This is why we can see those lights.
Also, this happens only due to the movement of energy level from one level to another. Electrons in atoms and molecules help to exchange energy.
These phenomena upon which some chemical mechanisms depend are human vision and plant photosynthesis. Both are based on white light.
White Colour Meaning in Electromagnetic Spectrum
All possible frequencies of electromagnetic radiation are coming under the electromagnetic spectrum. This is a collective term that extends from down to up frequencies.
These frequencies are used in modern-day transmission systems such as communication systems, home appliances, radio wave communication, and gamma radiation.
The colour of the light is quite normal and it is almost close to the infrared. These shortwaves have a higher frequency. It does travel up to thousands of kilometres by reducing into atoms.
Colour of Sunlight
You can understand the colour of the sunlight with a small demonstration.
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Apparatus Required for the Prism Experiment:
Place a glass prism inside a room. Try a dark room for this experiment.
Keep the prism in a position where the direct sunlight can fall upon its surface.
Make a proper hole in the window shutter of the room so that the sunlight can pass through the hole like a narrow beam.
Mount a paper sheet (white sheet) on the other side of the wall where the direct sunlight can fall on the prism and get the best result via the reflection.
What do you observe after this process? If you look carefully, the light splits into a spectrum of colours. The sunlight (white light) is having these colour combinations as violet, indigo, blue, green, yellow, orange, and red.
Scientists have named these combinations of colours as VIBGYOR. The letters in the word define each colour that is present in the sunlight.
Drawbacks That Won’t Allow Us to See All Seven Colors
At the entrance of sunlight to the earth’s atmosphere, it comes in the interaction with a lot of things such as air molecules, dust, pollution, and smoke. As we know, several colours of the spectrum have non-uniform wavelengths.
Also know that blue and violet have shorter wavelengths. They are very weak and finish at the bottom of the spectrum table. They can be easily scattered in the atmosphere.
During Noon
This is the time where the sun is just above us. The rays coming out of the sunlight have higher wavelengths and can cover the least distance. In this situation, the blue light is scattered.
During Morning or Evening
At this moment, the sun is near the horizon. This makes the light rays travel a longer distance through the earth’s atmosphere. Due to the horizon, the light rays have to go through a lot of interference that makes them scattered away.
Both of the time slots are not suitable enough to provide us with a vision so that we can easily perceive all seven colours coming out of sunlight.
FAQs on White Colour
1. What exactly is white colour in the context of Physics?
In Physics, white light is not considered a single colour but a combination of all the different colours present in the visible spectrum. When light containing all wavelengths of the visible spectrum in roughly equal proportions enters our eyes, our brain perceives this mixture as the colour white. Sunlight on a clear day is a primary example of white light.
2. What are the constituent colours of white light and in what order do they appear in a spectrum?
White light is composed of a continuous spectrum of colours, which are commonly grouped into seven main bands. When separated by a prism, they appear in a specific order based on their wavelength. This order is remembered by the acronym VIBGYOR:
- Violet
- Indigo
- Blue
- Green
- Yellow
- Orange
- Red
Violet has the shortest wavelength and red has the longest.
3. How can it be demonstrated that white light is made of seven colours?
The composition of white light can be demonstrated using a glass prism. When a narrow beam of sunlight (white light) is passed through a prism, it splits into its seven constituent colours. This phenomenon, known as dispersion of light, occurs because each colour travels at a slightly different speed within the prism and thus bends at a slightly different angle, separating them into a visible band of colours called a spectrum.
4. Why does a prism split white light into different colours?
A prism splits white light due to a principle called dispersion. The speed of light in a medium like glass depends on its wavelength (or colour). When white light enters the prism, each of its constituent colours bends (refracts). Since violet light has a shorter wavelength, it slows down more than red light (which has a longer wavelength). This difference in speed causes violet to bend the most and red the least, effectively separating the colours from each other.
5. If an object appears white, what does this tell us about how it interacts with light?
An object that appears white does so because its surface reflects all the wavelengths of the visible light that strikes it. Instead of absorbing any particular colour, it scatters all colours back. Since the combination of all colours of the spectrum is perceived as white by our eyes, the object appears white. This is different from a black object, which absorbs almost all wavelengths of light.
6. Is it possible to combine the seven colours of the spectrum back into white light?
Yes, the process of dispersion is reversible. Sir Isaac Newton demonstrated this by placing a second, identical prism in an inverted position next to the first one. When the band of seven colours (spectrum) produced by the first prism was passed through the inverted second prism, the colours recombined. A single beam of white light emerged from the other side, proving that white light is a mixture of these colours.
7. How is the concept of white light and its spectrum applied in the real world?
Understanding the spectrum of white light is crucial in many technologies and scientific fields. For example:
- Televisions and Displays: Screens use red, green, and blue (RGB) pixels that combine in varying intensities to produce white and millions of other colours.
- Astronomy: Scientists analyse the spectrum of light from distant stars, a technique called spectroscopy, to determine their chemical composition, temperature, and motion.
- Art and Photography: Artists and photographers manipulate the properties of light and colour to create specific moods and visual effects.
