SOLUTION

When a voltmeter is connected across a forward-biased diode it will read a voltage approximately equal to diode barrier potential.

Detailed Explanation

Once PN junction is formed and depletion layer created, further movement of charge carriers across the junction stops i.e. depletion layer acts as a barrier to the movement of charge carriers across the junction. There exists a potential difference across the depletion layer and is called barrier potential.

Forward bias breaks down the barrier or depletion region in a diode, and current flows through the diode. Bias is just another name for a DC voltage. Hence in the forward bias condition, the diode read voltage is approximately equal to barrier potential voltage.