Chapter 28.2, Problem 1TH

Consider the experiment shown in the figure at right. An evacuated tube contains two electrodes, A and B. Monochromatic light of $\lambda =250nm$ is incident on electrode B, which is made of nickel $\left(\varphi =5.2eV\right)$ .

When the voltage across the electrodes is zero volts, the ammeter reads zero current.

Would the ammeter read zero current or a non-zero current if you were to:

• Double the intensity of the light source? Explain.
• Increase the voltage across the electrodes from 0 V to $+5.5V$? Explain.
• Replace the nickel electrode with one made of aluminum $\left(\varphi =4.2eV\right)$? Explain.