Question

A red-glass piece is heated until it glows in dark. The colour of the glow will be:

• A. red
• B. orange
• C. green
• D. violet

Answer 1

Answer: (C)

green

The complementary colours are as follows:

• violet - yellow
  
• blue - orange
  
• green - red
  

Now, this means that a red coloured substance will emit green coloured light while glowing in dark.
Hence, the glass plate will appear green.