The answer to each of the following questions is a single-digit integer ranging from 0 to 9. Darken the correct digit.
A metal plate with total charge Q on it, is placed parallel to a dielectric slab of same area. Let q be the charge appearing on the surface of dielectric whose dielectric constant is 2. Calculate `Q//q`.

Explanation

To solve the problem, we need to find the ratio \( \frac{Q}{q} \), where \( Q \) is the total charge on the metal plate and \( q \) is the charge appearing on the surface of the dielectric slab.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a metal plate with a total charge \( Q \).
- This plate is placed parallel to a dielectric slab with a dielectric constant \( k = 2 \).

2. **Charge Induction on the Dielectric**:
- When a metal plate with charge \( Q \) is placed near a dielectric, it induces a charge \( q \) on the surface of the dielectric.
- The induced charge \( q \) can be calculated using the formula:
\[ q = Q \left(1 - \frac{1}{k}\right) \]
- Here, \( k \) is the dielectric constant of the material.

3. **Substituting the Dielectric Constant**:
- We know that \( k = 2 \).
- Substitute \( k \) into the equation:
\[ q = Q \left(1 - \frac{1}{2}\right) \]
- Simplifying this gives:
\[ q = Q \left(\frac{1}{2}\right) \]

4. **Finding the Ratio \( \frac{Q}{q} \)**:
- Now, we need to find the ratio \( \frac{Q}{q} \):
\[ \frac{Q}{q} = \frac{Q}{Q \left(\frac{1}{2}\right)} = \frac{1}{\frac{1}{2}} = 2 \]

5. **Final Answer**:
- Therefore, the value of \( \frac{Q}{q} \) is \( 2 \).

### Final Result:
\[ \frac{Q}{q} = 2 \]