6.2 Pioneers of Radiation

Question 1

How are X-ray produced?

Answer 1

When objects are radiated with energy, the electrons enter their excited. In this unstable state, they fall back to their ground state. This process produces X-rays.

Question 2

Contribution of Roentgen to the understanding of radioactivity / Principle of Crookes Tube? (3)

Answer 2

• Crookes tube
• Vacuumed
• Covered in black cardboard to prevent visible light from escaping
• 2 charged plates (cathode and anode) when connected with power, an electric current form which was visible and this is called a cathode ray.
• Crookes tube was producing an invisible and highly penetrating EMR which travelled through cardboard. He named this X-ray.

Question 3

How did Roentgen demonstrate the principle of X-ray?

Answer 3

X-rays could travel through low-density objects and are blocked by dense objects. Roentgen demonstrated this with his wife’s hand, where the flesh was transparent and the denser ring and bones were dark on the screen.

Question 4

Contribution of Beckequerel? (2)

Answer 4

• Discovered the phenomenon of fluorescence
• Found that some substances would glow when exposed to an energy source (eg. sunlight)
• Once the energy source is removed, the substance would stop glowing.
• Through accidentally exposing photographic plates, he deduced that uranium is radiating some form of invisible rays.

Question 5

How did the Curies discover polonium?

Answer 5

While experimenting with pitchblende, they discovered that even with the uranium removed, there was still leftover material which was more radioactive, thus they concluded that there was another element called polonium.

Question 6

Explain the difference between alpha and beta radiation (3)

Answer 6

• Alpha radiation is easily blocked or absorbed whereas beta radiation is more penetrating.
• Alpha particles are positively charged and contains 2 neutrons and 2 protons.
• Beta radiation were negatively charged electrons.
• They curve in different directions under a magnetic field.

Question 7

Explain Villard’s contribution (2)

Answer 7

• Studied radium radiation and discovered gamma rays, which were more penetrating than alpha and beta rays, and were similar to x-rays. Gamma rays were unaffected by the magnetic field, therefore wasn’t charged.