A: A metallic shield in the form of a hollow shell may be built to block an electric field.
R: In a hollow spherical shield, the electric field inside it is zero at every point.

Options

A. Both .A. and .R. are true and .R. is the correct explanation of .A.
B. Both .A. and .R. are tru and .R. is not the correct explanation of .A.
C. A. is true and .R. is false
D. A. is false and .R. is true

Answer

To solve the question, we need to analyze the statements given:

**Statement A:** A metallic shield in the form of a hollow shell may be built to block an electric field.
**Statement R:** In a hollow spherical shield, the electric field inside it is zero at every point.

### Step 1: Understanding the Concept of Electric Fields and Conductors
When a conductor is placed in an external electric field, charges within the conductor redistribute themselves. This redistribution creates an induced electric field that cancels the external electric field inside the conductor.

**Hint:** Remember that conductors allow free movement of charges, which is crucial for understanding how they interact with electric fields.

### Step 2: Analyzing Statement A
The statement A is true because a hollow metallic shield can indeed block external electric fields. This is a fundamental property of conductors.

**Hint:** Think about how the movement of charges in a conductor responds to external electric fields.

### Step 3: Analyzing Statement R
Statement R claims that the electric field inside a hollow spherical shell is zero at every point. This is also true due to the properties of conductors. When the shell is charged or subjected to an external electric field, the induced charges on the surface of the shell create an electric field that cancels out any external electric field within the hollow region.

**Hint:** Consider Gauss's law and how it applies to spherical symmetry in conductors.

### Step 4: Conclusion
Both statements A and R are true. However, the reasoning provided in the question might be misleading if interpreted incorrectly. The electric field inside a hollow conductor is indeed zero, but the statement does not imply that the electric field cannot exist outside the shell.

**Final Answer:** Both A and R are true, but the reasoning may need clarification.

### Summary of Steps:
1. Understand the behavior of electric fields in conductors.
2. Analyze the truth of Statement A.
3. Analyze the truth of Statement R.
4. Conclude the relationship between the statements.