8.1 Quarks Introduction

Question 1

Describe the experiment used to identify quarks. What other experiment is similar?

Answer 1

High energy electrons (and low energy) were shot at liquid hydrogen in the bubble chamber..

Question 2

What happened when the electrons were of low energy? What happened to the kinetic energy?
What was the suggestion?

Answer 2

The electrons were deflected by the protons forming the nuclei of the hydrogen. There was no net loss of Ek and so the collision was elastic.
It seemed like the positive charge was confined in a tiny volume.

Question 3

What happened when electrons were of high energy?

What was the conclusion?

Answer 3

The electrons lost Ek and the collision therefore was inelastic. The proton fragmented into a shower of particles rather then recoiling. The conclusion was that protons contained localised charge centres called quarks.

Question 4

When electrons were shot at high energy why was the collision inelastic?

Answer 4

The collision is said to be inelastic as energy was transformed into matter.

Question 5

What are the localised charge centres called?

Answer 5

Quarks

Question 6

What is an ‘up’ quark?

What is the symbol of this quark?

Answer 6

quarks with a charge of +2/3e

Symbol u

Question 7

What is a ‘down’ quark?

What is the symbol of this quark?

Answer 7

quarks with the charge of -1/3e

symbol d

Question 8

What did the experiment find about quarks?

Answer 8

We could not find any individual quarks.

Question 9

What were the showers of quarks?

Answer 9

Mesons - quark and antiquark pair

Question 10

What quarks are found inside a proton?

Answer 10

2 u and 1d

Question 11

What quarks are found inside a neutron?

Answer 11

2 d and 1 u

Question 12

How can we find the charge of the subatomic particle?

Answer 12

Add the charges of the quarks inside them.