which variable is directly proportional to frequency?\nposition\nwavelength\nvelocity\nenergy

Brief Explanations:

The energy of a photon is given by the formula (E = h\nu), where (h) is Planck's constant ((h = 6.626\times10^{-34}\space J\cdot s)) and (\nu) is the frequency of the photon. Since (h) is a constant, (E\propto\nu) (energy is directly proportional to frequency). Position has no direct proportionality relation with frequency. For a wave, (v=\lambda\nu) (where (v) is velocity, (\lambda) is wavelength and (\nu) is frequency). If (v) is constant (e.g., in a vacuum for electromagnetic waves (v = c)), then (\lambda\propto\frac{1}{\nu}) (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