frequency question?

Question

which has the higher frequency--

dim purple light [wavelength=400 nm]
OR
bright red light [wavelength=700 nm]

&
can you tell me how you know?

what about seeing which has higher amplitude?

Answer 1

The frequency of the light only relates to the color, with blue light higher frequency than red light. Therefore, the purple light will have the higher frequency regardless of brightness. Also, frequency is proportional to the reciprocal of wavelength, so longer wavelength (red) means lower frequency.