Question

The graph (fig A) illustrates the correlation between the number of protons (x-axis) and the number of neutrons (y-axis) for elements A, B, C, D, and E in the periodic table. These elements are denoted by the letters rather than their conventional symbols. When the element C, depicted in the graph, undergoes radioactive decay, it releases radioactive rays. When these rays are directed into the plane of the paper in the presence of a magnetic field, as indicated in the fig B, they experience deflection, causing them to move upwards.

Name the law used to identify the radioactive radiation emitted by the element.

Answer 1

In Figure B, a magnetic field is applied perpendicular to the direction of the radioactive ray. The ray is deflected upward, indicating the type of particle based on the direction of force.

According to Fleming’s Left-Hand Rule, the direction of motion (force) on a charged particle in a magnetic field depends on:

• Thumb → Force (motion)
• Forefinger → Magnetic field (North to South)
• Middle finger → Current (positive charge flow)

Since the particle is deflected upward, and it is moving into the plane of the paper, it must be positively charged, like an alpha (α) particle.

So, Fleming’s Left-Hand Rule helps in identifying the ray as positively charged, i.e., alpha radiation.