# A heated blue glass

When a piece of red glass is heated to high temperature, it glows green. Similarly, when a green glass is heated to high temperature, it glows red. But How does a blue or yellow glass glow when heated? I could not find the answers for this when I browsed.

## Answers and Replies

DaveC426913
Gold Member
When a piece of red glass is heated to high temperature, it glows green. Similarly, when a green glass is heated to high temperature, it glows red.
What evidence do you have of either of these claims?

DaveC426913
Gold Member
Ok, so instead of simply Googling for the answer, how about you apply some logic. Did you read the hint that suggests a relationship between the colour of the glass and the colour it will glow?

In the colour spectrum, what relationship do red and green have to each other?

Redbelly98
Staff Emeritus
Homework Helper
When a piece of red glass is heated to high temperature, it glows green. Similarly, when a green glass is heated to high temperature, it glows red. But How does a blue or yellow glass glow when heated? I could not find the answers for this when I browsed.
The room-temperature color of the glass refers to the wavelengths that are reflected. As a consequence, those same wavelengths are only weakly emitted when the glass is heated, while other wavelengths are strongly emitted. As the book explains, a lack of green in an otherwise white spectrum will appear red.

There is also the complication that, as an object is heated, it first glows predominately red, and then when heated further this shifts to a white color. Apparently the book is talking about these higher "white-hot" temperature levels for the glass.

DaveC426913
Gold Member
As the book explains, a lack of green in an otherwise white spectrum will appear red.

Right. So the question simply boils down to one of complementary colours.