A small metal ball is suspended in a uniform electric field with the help of an insulated thread. If high energy X-ray beam falls on it, then the
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → ball will be deflected in the direction of electric field
High-energy X-ray photons falling on the metal ball knock electrons out of it by the photoelectric effect. Losing electrons leaves the ball positively charged. A positive charge in an electric field feels a force \( \vec{F} = q\vec{E} \) along the field, so the ball is deflected in the direction of the electric field.
Why the other options are incorrect
Option (2) ball will be deflected in direction opposite to the direction of electric field — Incorrect. That would need the ball to become negatively charged; the X-rays remove electrons, so it becomes positive.
Option (3) ball will not be deflected — Incorrect. The ball stays undeflected only while it is neutral; once it loses electrons it feels a force.
Option (4) ball will oscillate — Incorrect. The ball gets a steady force in one fixed direction, so it settles in a deflected position rather than oscillating.