Exam Q 6

Question 1

Give one way of detecting the presence of cathode rays in a vacuum tube

Answer 1

Using a maltese cross that will cast a shadow
or
installing a paddle wheel in the middle of the vacuum chamber, the cathode rays will turn it as they move to the anode

Question 2

Name the scientist who identified cathode rays as subatomic particles

Answer 2

J J Thomson

Question 3

What was the name of the subatomic particles that J J Thomson identified?

Answer 3

Electrons

Question 4

Name one of the three scientists who won the noble prize in physics in 1903

Answer 4

Marie Curie/Pierre Curie/Henri Becquerel

Question 5

State 3 observations made by Rutherford’s team when they bombarded a thin sheet of gold with alpha particles

Answer 5

1. Most alpha particles were undeflected and passed through the sheet of gold
2. Some alpha particles were deflected at large angles
3. Very few alpha particles were reflected back along their original paths.

Question 6

Explain how Rutherford deduced that the nucleus was positive

Answer 6

The repulsion of positive alpha particles

Question 7

Explain how Rutherford deduced that the nucleus was small and dense

Answer 7

Most alpha particles were not deflected and passed through the thin gold foil.
some were deflected slightly as they passed through and some at large angles.
A few were reflected back along their paths

Rutherford concluded from his metal foil experiments that most of an atom is empty space with a tiny, dense, positively charged nucleus at the center that contains most of the mass of the atom