Final answer:
The violet line disappears from the spectrum because violet light is scattered widely in the Earth's atmosphere due to its short wavelength, along with the higher sensitivity of human eyes to blue light.
Step-by-step explanation:
The reason why the violet line may disappear from the spectrum is that violet light scatters more than other colors in the atmosphere. Despite violet light having the shortest wavelength, and therefore the highest frequency and energy in the visible light spectrum, it is scattered in all directions by the small molecules and particles in the Earth's atmosphere.
This scattering causes violet light to rarely reach our eyes directly, and the sky appears blue to us instead of violet because the human eye is more sensitive to blue light.
The violet line disappears from the spectrum because violet light scatters more than other colors in the atmosphere. Scattering is the process by which light is redirected in all directions by particles in the atmosphere. Violet light has the shortest wavelength and therefore scatters more easily compared to other colors.
Therefore answer is d) Violet light scatters more than other colors in the atmosphere.