(A): A small metal ball is suspended in a uniform electric field with an insulated thread. If high energy X-ray beam falls on the ball, the ball will be deflected in the electric field.
(R ): X-rays emits photoelectron and metal becomes negatively charged.

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 given question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that a small metal ball suspended in a uniform electric field will be deflected when a high-energy X-ray beam falls on it.
- The ball is suspended with an insulated thread, which means it can move freely without any interference from other forces.

2. **Effect of the Electric Field**:
- In a uniform electric field, a charged object experiences a force. The direction of this force depends on the sign of the charge.
- The force acting on the ball can be described by the equation \( F = Q \cdot E \), where \( F \) is the force, \( Q \) is the charge on the ball, and \( E \) is the electric field strength.

3. **Impact of the X-ray Beam**:
- When a high-energy X-ray beam strikes the metal ball, it can cause the emission of electrons from the surface of the metal. This phenomenon is known as the photoelectric effect.
- The emitted electrons are referred to as photoelectrons.

4. **Charge of the Metal Ball**:
- As electrons are ejected from the metal ball due to the X-ray beam, the ball loses negative charge (electrons).
- Consequently, the metal ball becomes positively charged because it has lost negatively charged electrons.

5. **Deflection of the Ball**:
- Since the ball is now positively charged, it will experience a force in the direction of the electric field.
- Therefore, the ball will be deflected in the electric field due to its positive charge.

6. **Understanding the Reason (R)**:
- The reason states that X-rays emit photoelectrons and that the metal becomes negatively charged.
- However, this statement is incorrect. While X-rays do emit photoelectrons, the metal ball becomes positively charged due to the loss of these electrons, not negatively charged.

7. **Conclusion**:
- The assertion (A) is true: the ball will be deflected in the electric field.
- The reason (R) is false: the metal ball does not become negatively charged; it becomes positively charged.

### Final Answer:
- Assertion (A) is true.
- Reason (R) is false.