Question

which variable is directly proportional to frequency?
position
wavelength
velocity
energy

Explanation:

According to the Planck - Einstein relation \(E = h
u\) (where \(E\) is energy, \(h\) is Planck's constant, and \(
u\) is frequency), energy is directly proportional to frequency. Position has no direct proportionality relation with frequency. The relation \(v=\lambda
u\) (where \(v\) is velocity, \(\lambda\) is wavelength) shows velocity is a product of wavelength and frequency (not direct proportionality in a simple sense as here \(v\) is constant for light in a vacuum and \(\lambda\) and \(
u\) are inversely proportional).

Answer:

energy