Question

Which of the wavelengths $4000\stackrel{o}{A}$ and $8000\stackrel{o}{A}$ has a higher frequency?

Answer 1

Speed of electromagnetic wave $v=3\times {10}^{8}m/s$ in vacuum.
Frequency of wave $\nu =\frac{v}{\lambda }$
$⟹\nu \propto \frac{1}{\lambda }$ $(\because v=same)$
This means higher the wavelength of light, lower is the frequency.
Thus $4000A^o$ light has higher frequency than $8000A^o$ light.