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What Color Light is Transmitted By a Piece of a Blue Glass | (Science of Color)

When light passes through a certain medium, it changes its color. Why? Light in fact doesn’t change its color, it tends to lose a few colors. When we see sunlight, it appears white. But it’s not the case actually. White light or sunlight is a mixture of six basic colors. These colors are arranged in a specific order: red, orange, yellow, green, blue and violet.

When you place a colorful medium in the path of light, only those colors are reflected and are not absorbed. Every pigment of light color has the ability to absorb certain colors and reflect others. Suppose you place a blue color glass in the path of light, what happens? Let’s read the answer to the question.

What color of light is transmitted by a piece of blue glass?

The blue glass absorbs green and red light from the spectrum. It reflects blue light only. That’s why it appears to be blue in color. While yellow light absorbs red and green and transmits yellow color. This is the main reason why yellow pieces of glass appear to be yellowish in color.

Whatever light is not transmitted, it is absorbed in the medium. Colored glass is transparent in the sense that it does not contain real color pigmentation. It has filters of a particular color that makes it look colorful.

Handy Hints: What happens if you swallow a glass?

What Color of Light Is Transmitted By a Piece of Blue Glass: Physics of Colors

Colored glass is not colored in the actual sense. It is a filter that is largely transparent. The colored glass has the ability to absorb certain frequencies of light or some colors. When light passes through glass, its transmission of certain colors depends on different factors

Factors that affect the transmission of colors from blue glass

  1. Source of Light
  2. Thickness of Glass
  3. The way glass itself is colored

Depending on all these factors blue glass potentially transmits blue light or yellow light. It absorbs green and red colors effectively. In most cases when sunlight passes through blue glass, it transmits blue color only. 

You may have observed blue-colored windows in your room. They only reflect blue light to keep the rooms cool.  This color is famous as a cool color. So, blue glass is widely used in windows.


When white light or sunlight hits the blue glass, the blue pigment absorbs red and green colors. Now the remaining colors are yellow and blue. Resonance occurs when the electrons in the blue glass vibrate more intensely than in normal conditions. As a result, red and green would absorb and only blue would pass through the blue color glass. For more explanation, you can read color subtraction. 

Hence blue glass absorbs all other wavelengths. It may be of a single frequency or could be of a combination of frequencies

We can’t say blue is not absorbed by the blue glass. In fact, the blue color is first absorbed and then re-emitted. Because of this re-emission, it transmits blue color light only. While other colors like green and red are absorbed first and then not emitted. 

 Why are other wavelengths of colors not re-emitted from glass?

The other colors raised the energy level of atoms on the surface. Instead of emitting outside, they will raise the temperature of the medium of glass itself. But they will radiate soon to 360 degrees.

What Colour or Colours of Light are Transmitted by a Piece of Yellow Glass

A yellow piece of glass will transmit red and green light. It reflects yellow light, that’s why we see it yellow. Whatever wavelength of light is not absorbed will be transmitted. Glass is itself transparent. It uses filters of colors. Whatever light is reflected from yellow glass depends mainly on the light source. 

What Color Does Blue Transmit

Blue transmits only blue color. That’s why it looks blue. It absorbs the green and red color spectrum. When white light strikes a blue object, the red, green, and yellow colors of its visible spectrum are absorbed by the blue color. The color which is not absorbed is blue.

When Does White Light Shine on Blue Glass, Which Colors Make it Through The Glass?

When white light sheds on blue glass, a part of it is absorbed and the rest is transmitted. The absorbed portion includes red and green colors. While the reflected portion includes blue color. This is the main reason that blue glass appears to be blue to the eyes.

What Happens to Light If an Object is Blue?

When light hits the object with blue color a part of it is reflected. The reflected portion of light has a color that is not absorbed by the blue pigment of the object. It is normally blue. Blue actually appears blue because it transmits the blue color of the visible spectrum.

What Happens When White Light Passes Through a Blue Filter

When white light passes through a blue filter, it absorbs all colors except blue. Red, green and yellow are absorbed in the filter. Only blue passes through it. So we can see the blue filter as blue. 

Last Lines

It’s evident from the above post that a blue piece of glass transmits blue color light only. If the thickness of the glass material is more than usual, this light color may turn dark blue. If you want to experiment with this at home, place a blue filter under the glass and let the light pass through it. Turn off the lights in the room. You will see only blue light pass through the glass. The rest of the colors are absorbed. 

Its concluded:

“The color of light is not in the object. It’s rather present in the light which reflects off and transmits through the object.”