Final answer:
A more energetic transition in the mercury atom compared to the green light emission would result in ultraviolet light emission, which has a higher energy than visible light.
Step-by-step explanation:
A more energetic transition in the mercury atom compared to the green light emission would emit a photon with a higher energy. Since the sequence of light in terms of increasing energy goes from infrared to visible to ultraviolet light, ultraviolet light would be more energetic than visible green light. Therefore, the correct answer is b) Ultraviolet light. This is founded on the understanding that the electromagnetic spectrum is ordered by frequency and energy, with infrared having the least energy, visible light (like red, green, and blue) having more, and ultraviolet having even more energy per photon.