Chapter 24 Particle Physics

Question 1

explain the alpha-particle scattering experiment

Answer 1

Narrow beam of alpha particles, all same Kinetic Energy, from a radioactive source.

Targeted at a thin sheet of gold only a few atomic layers thick.

Alpha particles were scattered by the foil and detected on a zinc sulfide screen mounted in front of a microscope.

Each alpha particle hitting the fluorescent screen produced a tiny speck of light.

Microscope was moved around in order to count the umber of alpha particles scattered through different values.

Question 2

Observations of the alpha-particle scatter experiment

Answer 2

most alpha particles passed straight through

or were deflected slightly

only 1 in 800 deflected greater than 90 degrees.

Question 3

Conclusions from the alpha-particle scatter experiment

Answer 3

the atom must have a nucleus which is very DENSE, SMALL and POSITIVELY CHARGED.

rest of the atom is almost entirely empty space.

Question 4

define the electronVolt

Answer 4

Ek gained by an electron when it accelerates through a P.D of 1V