Correct option is B
A sodium vapor lamp emits nearly monochromatic light, primarily in the yellow part of the visible spectrum, around 589 nm.
This monochromatic emission is due to the excitation of sodium atoms, which emit light at a specific wavelength.
This characteristic makes sodium vapor lamps efficient for specific applications, such as street lighting, where a uniform color is preferred.
Advantages
High luminous efficacy.
Long lifespan.
Suitable for outdoor lighting applications like street lighting and industrial lighting.
Disadvantages
Poor color rendering index (CRI) compared to other types of lamps.
Requires a warm-up time to reach full brightness.
