Two radio antennas A and B radiate in phase at a frequency of 15 MHz. Antenna B is 120 m to the right of antenna A. Consider point Q along the line connecting the antennas, a horizontal distance x to the right of antenna A. The frequency, and hence the wavelength, of the emitted waves can be varied. Required:
a. What is the longest wavelength for which there will be destructive interference at point Q?
b. What is the longest wavelength for which there will be constructive interference at point Q?

  distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

  slope of a graph = change in value of y -axis / change in values of x -axis

  comparing both the equations

    change in value of y -axis = change in position

  change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.