Correct option is A
Monochromatic light is electromagnetic radiation that has a single wavelength or frequency. When this frequency is part of the visible spectrum, it's called monochromatic light.
Sodium Vapour lamp-
· These lamps are used for wattage up to 40, 60, 85 and 140 watts.
· They produce 50 to 70 lumens per watt of light.
· It's working life is about 3500 hours.
· It is used for street lighting and in industrial establishments for security purpose at night.
· This lamp works on 220 Volt AC.
· The light given by sodium vapor lamps is yellow.
