A beam of ultraviolet light is incident on the metal ball of an electroscope that is initially uncharged. Does the electroscope acquire a charge?

Options

A. Yes, it acquires a positive charge
B. Yes, it acquires a negative charge
C. No, it does not acquire a charge
D. Its acquiring the charge depends on the work function of the metal

Answer

To determine whether the electroscope acquires a charge when a beam of ultraviolet light is incident on its metal ball, we can follow these steps:

### Step 1: Understand the Electroscope
An electroscope is a device used to detect electric charge. It consists of a metal ball connected to thin metal leaves. When charged, the leaves repel each other and spread apart.

**Hint:** Recall the basic function of an electroscope and how it indicates charge presence.

### Step 2: Consider the Effect of Ultraviolet Light
Ultraviolet (UV) light consists of photons, which can impart energy to electrons in the metal of the electroscope. This interaction can lead to the photoelectric effect, where electrons are ejected from the metal surface if the energy of the incoming photons is sufficient.

**Hint:** Think about how light interacts with matter, particularly in terms of energy transfer.

### Step 3: Determine the Conditions for Electron Ejection
For the photoelectric effect to occur, the energy of the UV light photons must exceed a certain threshold known as the work function of the metal. The work function is the minimum energy required to eject an electron from the metal surface.

**Hint:** Remember that not all light has enough energy to cause electron ejection; it depends on the frequency of the light.

### Step 4: Analyze the Outcome
If the energy of the UV light is greater than the work function of the metal, electrons will be ejected from the metal ball. This loss of negatively charged electrons will leave the electroscope with a net positive charge.

**Hint:** Consider what happens to the charge of the electroscope when electrons are removed.

### Step 5: Conclusion
If the UV light has sufficient energy (greater than the work function), the electroscope will acquire a positive charge due to the ejection of electrons. If the energy is insufficient, no charge will be acquired.

**Hint:** Reflect on the relationship between energy, electron ejection, and charge acquisition.

### Final Answer
The electroscope will acquire a positive charge if the energy of the ultraviolet light is greater than the work function of the metal. If the energy is less, it will not acquire any charge.