14.Choose first dot 1: 6 wavelength from S1 and 4 wavelength of S2, hence pd = 2wavelength. You may also use a ruler to measure as the diagram is drawn to scale. ie. 6cm - 4 cm = 2 cm corresponding to 2 wavelengths.
Dot 2: 4.5 wavelength for S1 and 3 wavelength from S2, hence pd = 1.5 wavelength.
The remainder dots are 1.5, 2.0, 2.0, 1.0, 2.0, 1.5 wavelengths.
To draw the 1st minima , link up all points that are 0.5 wavelength on one side of the axis . Repeat for the other side of the axis. To help you see , identify the n=1 and n=0 maxima line (the axis) , the 1st minima is in between.
15. When switch is Open it measure e.m.f and when it is closed the terminal p.d. c) The energy lost as heat is I2rt, where r is the internal resistance of the battery. d) If R is increased , current is reduced hence heat loss is reduced.
