Question

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

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 \(c=\lambda
u\) (where \(c\) is the speed of light, \(\lambda\) is wavelength and \(
u\) is frequency) shows that wavelength is inversely proportional to frequency. Velocity of a wave (for electromagnetic waves \(c = \lambda
u\), for mechanical waves \(v=\lambda
u\)) is not directly proportional to frequency as it also depends on wavelength.

Answer:

energy