**Category:** Optics  
**Subtype:** Interference  
**Problem Description:** This problem involves the interference of light waves, specifically using the Yound's double-slit experiment. It asks for the relationship between the number of bright fringes (or bands) observed for two different wavelengths of light (red and blue) when a certain number of blue fringes are counted. The goal is to determine how many red fringes correspond to the 6 blue fringes counted.