Which Color of Light Red or Blue Travels Faster in Crown Glass? (Scientific Interpretation)

Wondering to know about the physics of light and color? How does it react when it passes through glass? Obviously, light can pass through glass. However, a part of the light will be reflected after hitting the surface of the glass. But much light will pass through it. 

Light is not a single entity. It is composed of a spectrum of visible colors. These colors vary considerably in wavelength and hence speed as light passes through a certain medium.

Suppose we are going to experiment: Which color of light travel red or blue travel faster in crown glass?

The color with the highest wavelength passes faster in the crown glass. The red color has a high wavelength as compared to the blue color. That’s why red passes more quickly without bending more from crown glass. While blue has a lower wavelength and passes relatively slow. However, the slowest color that passes through crown glass is violet.

If you want scientific proof of this fact, keep reading till the end!

Handy Hints: What happens if you swallow glass?

What is Crown Glass

It is a unique variety of glass composed without lead or iron. It is actually made up of silicate soda or potash and lime. It acquires a crown-like shape in the blowing process. That’s why it is called crown glass. Scientifically, it is an optic glass of low dispersion and low refractive index.

What is crown glass used for? Earlier, it was used in windows. But due to the low refractive index, It has been now widely used in optics. It is also used in combination with flint glass to form lenses corrected for chromatic aberration.

Which Color of Light Travel Faster In Crown Glass Red or Blue: Scientific Interpretation

You may have encountered this multiple-choice in your exam

Which color of light travel faster in glass:

a) Red

b) Blue

c) Violet

Let’s see the scientific interpretation of the answer to this question.

Start with the equation:

The velocity of light as it passes through a certain medium is equal to:

v= fλ

In this equation:

 V stands for Velocity

f  Stands for frequency


 λ0 is the wavelength of light in a vacuum.

n is an index of refraction

From the first equation, we got that f is constant for any given color of light. It will not change with the change of medium

The visible spectrum of light when it passes through any medium is:

VIBGYOR= Violet, Indigo, Blue, Green, Yellow, Orange and Red

Hence light becomes from least wavelength to greater wavelength

It means colors with longer wavelength will move faster in any medium as compared to the shorter wavelength.

which color of light red or blue travels faster in crown glass

Table Of Wavelength of Visible Light Spectrum

Red625 – 740
Orange590 – 625
Yellow565 – 590
Green520 – 565
Blue435 – 500
Violet380 – 435

It is obvious from the above table that the wavelength of red color is greater than blue, violet and green. 

From the equation it is obvious speed is directly proportional to wavelength. The Color with a longer wavelength will travel faster than shorter wavelengths in any medium with n>1.

It means red has the longest wavelength so it will travel faster than blue or any other color.

Violet will travel the slowest.

Red will travel faster than blue.

Blue will travel slower than red but faster than violet.

Why Red Colour Light Travel Faster In Crown Glass Than Blue

When light travels in the crown glass its speed is 122000miles/second or 1.67*10^8.

When light enters in any medium with refractive index n>1 it slows down. It travels 1.8 times slower in glass as compared to vacuum. During passing through a medium like glass, light disperses into colors. The visible color spectrum constitutes red, orange, yellow, green-blue, and violet color.

The velocity or speed of light color from the visible spectrum in any medium depends on its wavelength. The greater the wavelength of the color, the faster it will travel through a medium. The smaller the wavelength of color the slower it will pass through a medium(crown glass)

Considering this fact red light travels faster in crown glass as compared to blue. Red light has a larger wavelength that makes it travel with high speed through a medium like crown glass. Blue color has a smaller wavelength than makes tit travel slowly inside the medium (crown glass).

Consider this table.

                         Index of Refraction For Borosilicate Crown Glass

ColourWavelengthIndex Of Refraction

Which Color of Visible Light Spectrum Travel The Fastest In Crown Glass

The visible light spectrum constitutes red, orange, yellow, green, blue and violet colors. All these colors have wavelengths as they pass through any medium. They reflect according to the reflective index and their wavelength. The greater the wavelength the faster they will travel

Red color travels fastest in crown glass as it has the largest wavelength( 625 – 740). Blue travels at a speed lower than red. Violet travels with the least speed or lowest speed from crown glass. 

What Color Does Light Red or Blue Travel Faster Than Crown Glass, Their Speeds Equal in The Index of Refraction Blue But Only if the Glass is Thin Red?

Red light travels faster than blue because of the slow index of refraction. Blue light has a high index of refraction that’s why it travels slower than red light in crown glass. The speed of light color in any medium is inversely proportional to the index of refraction. 

What Color Travels Slower in Crown Glass?

Violet color travels with the least speed in the crown glass. This color has a higher reflective index as it enters the glass medium. Moreover, it has the lowest wavelength that makes kt travel slowly. This color is at the bottom of the visible light spectrum.

Which Colour Has The Highest Velocity?

The red color has the highest velocity in the visible light spectrum.  Violet has the lowest velocity. Blue has comparatively higher velocity but not much than red. The velocity of light colors is determined by has formula v=fλ

Final Words

When light enters in mediums of high density to low density, its speed appears to increase. It also changes its path and bends in different directions.

Light is further made up of colors of different wavelengths. Each color reflects differently. Colors with smaller wavelengths are more sharp and slow when entering from air into glass. That’s why they bend mostly. While colors with larger wavelengths like red bent the least. 

To conclude, red is the fastest color to travel in the crown glass. Blue is not much faster than red. Violet is the slowest color to travel in a crown glass.

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