For this experiment you change the circuit slightly. You replace the bulb with an 1 kΩ resistor. Now measure the forward voltage which is applied to the diode.
In fact, you measure a forward voltage VF of...
VF = 0.7 V
This voltage depends mainly on the materials used in the diode (More on that later).
Here you have met the first departure from the model of the ideal diode. You will see, however, this was not the last departure...
In the next step, you look at the reverse voltage.