Question

which wavelengths are scattered when the sun is furthest to a ground - based observer? select two
highest frequency
long wavelength
short wavelength
lowest frequency

Explanation:

When the Sun is farthest from a ground observer (e.g., sunrise/sunset), sunlight travels a longer path through Earth’s atmosphere. Rayleigh scattering (dominant here) is inversely proportional to the 4th power of wavelength ($\propto \frac{1}{\lambda^4}$), so short wavelengths scatter more. Short wavelength corresponds to highest frequency (since $c = \lambda f$, so $\lambda \propto \frac{1}{f}$). Thus, highest frequency and short wavelength are scattered.

Answer:

highest frequency, short wavelength