Quantum Theory

Question 1

What did Einstein do with Planck’s discovery?

Answer 1

• explained photoelectric effect
• blue light gives off electrons at low energy, red light never does
• because red light contains higher energy particles

Question 2

What did Bohr discover about atoms?

Answer 2

• asked why electrons don’t spiral into centre of atom

- electrons jump between orbits. Quantum leaps.

Question 3

What happens with double slit experiments?

Answer 3

• electrons fired through act like both waves and particles depending on how many slits are open.
• cannot predict which slit they will enter.

Question 4

What does Heisenberg’s uncertainly principle say?

What are the implications?

Answer 4

• Cannot accurately know the position and velocity of a particle at the same time.
• we cannot speak of laws, just probabilities
• we cannot know causes
• the microscopic world works on different rules than visible world, eg tennis ball can’t pass through two slits at once.

Question 5

What is Bohr’s complementarity theory?

Answer 5

• we can see elections as waves and particles
• this is an analogy: two ways of looking at the same thing
• neither can be fully described or fully demonstrated at the same time

Question 6

What did de Brogile say about waves and particles?

Answer 6

• if light can be both, why can’t matter which is made up of atoms?

Question 7

What is Schrodinger’s wave function theory?

Answer 7

• described the quantum state of a particle

- with Born, gives likelihood of possible locations for a particle

Question 8

What is the Copenhagen interpretation?

Answer 8

The act of observation collapses the waveform, fixing one possible outcome.

Question 9

Criticisms of the Copenhagen interpretation ?

Answer 9

• Schrödinger’s cat.
• Everett III - many worlds interpretation. We merely observe one outcome relative to the universe we are in
• consistent histories interpretation - assigns probability to all possible histories, but doesn’t mean that they exist.

Question 10

What did Max Planck do?

Answer 10

• researching energy emitted by hot bodies
• found that energy is not given off in a constant stream as wave theory suggested
• energy released in packets, or quanta.