Q. Consider the following statements about sodium vapour lamp and mercury vapour lamp:

1. Sodium vapour lamp gives yellowish illumination, while mercury vapour lamp gives white illumination.
2. The light of sodium vapour lamp is due to atomic emission, whereas in mercury vapour lamp it is due to fluorescence emission.

Which of the above statements is/are correct?
Answer: Both 1 and 2
Notes: Both statements are correct. Sodium vapour lamps emit a characteristic yellow light due to atomic emission of sodium. Mercury vapour lamps primarily emit ultraviolet light, which excites the phosphor coating inside the lamp, resulting in visible white light due to fluorescence emission. Thus, there is a fundamental difference in their emission mechanisms and their light color.