To demonstrate the photoelectric effect, an electroscope is charged with electrons. Light from a flashlight is focused on the electroscope. An ultraviolet (UV) light is subsequently used in the same experiment. The intensity of both types of light can be increased or decreased.

1.

Describe what is observed in these two cases (using the flashlight and using UV light) in terms of a possible characteristic of light. Your description should include the results of the experiment when each type of light is used as well as why this result occurs.

2.

Explain what conclusion about the nature of light is drawn from this experiment and why results support this conclusion as opposed to a different conclusion about the nature of light.

3.

If the experiment was repeated again with the electroscope positively charged, what do you predict would happen? Explain your reasoning behind your prediction.