To illustrate the basis for our graphical approach, let us set 1/diequal to y, 1/doequal to x, and 1/fequal to b, so that Eq. 3 becomes:y = -x + bEq. 4 which is clearly, the equation of a straight line. The slope of this line is equal to -1and its y-interceptbequals 1/f. If we plot y(that is, 1/di) against x(that is, 1/do), we should get a downward slopingstraight line that intercepts the y axis at b (that is, 1/f). Note that the x-intercept also equals 1/f. Wetherefore have a graphical method for determining the focal length of our converging lens.Procedure: 1.Attach the light source assembly on the track. Position it so that the pointer at the base is at the2cm mark and the light source faces the other end of the track. 2.Turn the light source wheel until the number “4" is visible in the opening. This will be the“object” for this experiment. Note that the height of the object hois 2.0cm.3.Place the 20cm bi-convex lens at the 35cm mark. 4.Place the screen at the 120cm mark of the track so that the light from the light source passesthrough the lens and strikes the screen.