Question

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

Explanation:

The energy of a photon is given by the formula \(E = h
u\), where \(h\) is Planck's constant (\(h = 6.626\times10^{-34}\space J\cdot s\)) and \(
u\) is the frequency of the photon. Since \(h\) is a constant, \(E\propto
u\) (energy is directly proportional to frequency). Position has no direct proportionality relation with frequency. For a wave, \(v=\lambda
u\) (where \(v\) is velocity, \(\lambda\) is wavelength and \(
u\) is frequency). If \(v\) is constant (e.g., in a vacuum for electromagnetic waves \(v = c\)), then \(\lambda\propto\frac{1}{
u}\) (wavelength is inversely proportional to frequency). Velocity of a wave in a medium is a property of the medium (for a given medium, it is constant for a range of frequencies in non - dispersive media), so it is not directly proportional to frequency.

Answer:

energy