[Physics Class Notes] on White Colour Pdf for Exam

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. 

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.