Quanta

Question 1

What does quantum mechanics explain?

Answer 1

experimental observations that can not be explained by classical physics

Question 2

What experimental observations can quantum mechanics explain?

Answer 2

• blackbody radiation
• photoelectric effect
• emission and absorption spectra
• atomic structure
• electron diffraction

Question 3

What is a black body?

Answer 3

a surface that absorbs all wavelengths of electromagnetic radiation

Question 4

What is blackbody radiation?

Answer 4

the continuous spectrum of radiation that a black body emits

Question 5

What does the amount of black-body radiation emitted at any frequency depend on?

Answer 5

only temperature

Question 6

What is specific intensity a measure of?

Answer 6

the radiation emitted by a body

Question 7

How can energy be emitted or absorbed?

Answer 7

in discreet packets of energy called quanta

Question 8

What are the results of the photoelectric effect?

Answer 8

• the non-emission of electrons with very bright but low frequency radiation on a metal surface
• the increase in the speed of the emitted electron with frequency but not with intensity, increasing intensity only increases the number of electrons

Question 9

What equation is the energy of a photon given by?

Answer 9

E=hf

Question 10

What is wave-particle duality?

Answer 10

the phenomenon that describes the fact that electrons can act as both particles and waves

Question 11

What is the apparent wave-like behaviour of a particle related to?

Answer 11

its momentum

Question 12

What is true about an electron in quantum mechanics?

Answer 12

it does not have an exact position

Question 13

What is quantum mechanics?

Answer 13

the ability to calculate probabilities but not make specific, definite predictions

Question 14

What does the double-slit experiment demonstrate?

Answer 14

that light displays wave-like properties

Question 15

What is the result of the double-slit experiment using photons?

Answer 15

it could be concluded that the single-particle must somehow pass through both slits

Question 16

What is the result of the double-slit experiment?

Answer 16

we can conclude that the wave and particle properties can’t be measured at the same time

Question 17

Conclusions of the double-slit experiment?

Answer 17

• we cannot predict the exact path that either an electron or photon will follow
• we cannot make a direct measurement of the particles locations as this will interfere with the outcome of the experiment
• we can predict the probability the electron or photon has of landing at a particular point on the screen

Question 18

What can be said about the maxima of waves?

Answer 18

this is where there is a high probability of many electrons/photons arriving thus we see a bright patch

Question 19

What does Heisenberg’s Principle Uncertainty state?

Answer 19

The uncertainty principle says that we cannot measure the position (x) and the momentum (p) of a particle with absolute precision.

Question 20

What are the other quantities that can be used to demonstrate Heisenberg’s uncertainty?

Answer 20

energy and time

Question 21

What is quantum tunnelling?

Answer 21

A quantum particle can exist in a position that, according to classical physics, it has insufficient energy to occupy

Question 22

What are cosmic rays?

Answer 22

high energy particles arriving at the earth which have originated elsewhere

Question 23

Where do cosmic rays come from?

Answer 23

• the lowest energy cosmic rays come from the sun

* the intermediate ones come from elsewhere in the milky way and are often associated with supernovae

Question 24

When does a cosmic air shower happen?

Answer 24

when cosmic rays reach earth they combine with particles in the Earth’s atmosphere thus resulting in cosmic air

Question 25

What is solar wind?

Answer 25

a constant stream of particles emitted from the sun

Question 26

What are solar flares?

Answer 26

explosive releases of energy that radiate over virtually the entire EM spectrum

Question 27

What does the Earth’s magnetic field protect it from?

Answer 27

solar wind

Question 28

What is the cavity dominated by the Earth’s magnetic field called?

Answer 28

the magnetosphere

Question 29

What equation gives the force acting on a charge through a magnetic field?

Answer 29

F=qvB

Question 30

Why does a particle have a helical motion in a magnetic field?

Answer 30

The perpendicular component provides the central force, which produces uniform circular motion
The component parallel to the magnetic field does not cause the charge to experience a magnetic force so it continues to move with constant velocity in that direction

Question 31

Under what conditions would a charge in a magnetic field have a helical path?

Answer 31

if the charge moves at an angle to the magnetic field

Question 32

Explain why an ion follows a semi-circular path

Answer 32

it has a central force acting on it

Question 33

Why do charged particles approaching earth in the same direction not cause an aurora above the equator?

Answer 33

the particles never reach the atmosphere above the equator

Question 34

In what terms can quantum particles be talked about?

Answer 34

in terms of probabilities and not certainties

Question 35

If the time taken for an event is not known precisely then how will this affect the uncertainty in the energy associated with the event?

Answer 35

the uncertainty in energy will be low