Particles and Quantum Phenomena

Question 1

What are isotopes?

Answer 1

Same proton number but different number of neutrons.

Question 2

What is specific charge?

Answer 2

Charge per unit mass.

Question 3

What are ions?

Answer 3

Loss or gain of 1 or more electrons.

Question 4

Strong Nuclear Force and Range

Answer 4

-Only attractive between 0.5 fm and 3 fm.
-Repulsive less than 0.5 fm.
More than 3 fm its weak/ short range.

Question 5

What are EM waves (electromagnetic waves)?

Answer 5

-They are transverse waves.
-They oscillate perpendicular to each other and the direction of travel.

Question 6

What are the Orders of EM waves?

Answer 6

Lowest Frequency, Highest Wavelength:
-Radio
-Microwave
-Infrared
-Visable Light
-Ultraviolet
-X-rays
-Gamma Rays
**Highest Frequency, Lowest Wavelength

Question 7

What is eV?

Answer 7

Unit for energy.

Question 8

How do you convert from eV -> J?

Answer 8

EV-> J is dividing by 1.6x10^-19.

Question 9

How do you convert to eV-> J?

Answer 9

By multiplying eV by x1.6x10^-19

Question 10

What are Photons?

Answer 10

A quantised packet of EM energy.

Question 11

What is rest mass?

Answer 11

Mass of an object/ particle when it’s stationary.

Question 12

What is rest mass energy?

Answer 12

Energy equivalent to the mass of a stationary particle.

Question 13

What is pair production?

Answer 13

When a high energy photon converts into the particle and antiparticle.

Question 14

What is annihilation?

Answer 14

When a particle and antiparticle collide there masses are converted into energy in the form of 2 gamma photos travelling in the opposite direction to conserve momentum.

Question 15

What is the Strong nuclear force?

Answer 15

• Strongest
  -Hadrons only
  -Holds nucleus together
  -Short range 3fm.
  -Strange particles produced.
  Exchange Particle:
  -Gluon and Pions

Question 16

What is the Electromagnetic Force?

Answer 16

-Acts on charged particles.
Exchange Particles
-Virtual Photons

Question 17

What is the weak nuclear force?

Answer 17

-Acts on a particle.
-Very short range (0.001 fm)
-Causes radioactive decay.
Exchange Particles:
-W Boson.

Question 18

What must all been conserved?

Answer 18

-Momentum
-Energy
-Charge
-Baryon Number
Lepton Number

Question 19

What is intensity?

Answer 19

Power per unit area.

Question 20

What is the photoelectric effect?

Answer 20

Emission of electrons from a metal surface when light above a threshold frequency is incident on the metal.

Question 21

What is the work function?

Answer 21

The minimum energy required for an electron to escape from a metal.

Question 22

What is the threshold frequency?

Answer 22

Minimum frequency of light which causes electrons to be emitted from the surface of a metal.

Question 23

How to change the maximum kinetic energy?

Answer 23

Increasing the frequency, decreases the wavelength.
Effect:
-Electron comes out with a higher max energy.

Change the metal!
-lowers work function
Effect:
-Minimum energy for an electron to escape will be lower comes out with a higher kinetic energy.

Question 24

Why are electrons emitted with a range of kinetic energies up to a maximum?

Answer 24

-Delocalised electrons in metal have a range of energies.
-Electrons near the surface have the most energy therefore require the least to escape.
-Emitted with the highest kinetic energy.
Electrons deeper in the metal have the less energy so require more energy to escape the metal.

Question 25

Same wavelength, more intensity of light.

Answer 25

Effect:
-More electrons emitted
-Photon has same energy

Question 26

What happens when you increase brightness without a colour change and explain the effect of electron emitted?

Answer 26

• Number of photons increased.
• It’s a 1 to 1 interaction.
• More electron emitted.
• Same energy therefore work function unchanged.
  -Maximum kinetic energy of electrons doesn’t change.

Question 27

What happens when wavelength decreases without changing intensity? Explain why current increases then decreases as wavelength is shortened.

Answer 27

• Wavelength decreases, energy of the photon increases.
• More electrons are emitted.
• Electrons are emitted with maximum kinetics energy.
• Intensity is constant,photons number per time must decrease.

Question 28

What is ionisation by collision?

Answer 28

• Collision of free electrons with atomic electrons.
• Free electron transfers its kinetic energy to the atomic electron.
• Atomic electro now has enough energy to leave the atom completely.
• A charged atom is formed.

Question 29

What is ionisation by photon?

Answer 29

• Atomic electron absorbs energy from a photon.
• Enough energy from photon for an electron to leave the atom.

Question 30

What is excitation by collision?

Answer 30

• Collision of free electrons with atomic electrons.
• Free electron transfers all kinetic energy to atomic electron.
• Energy gained corresponding to the difference in energy levels.
• Atomic electron moves to a higher energy level.

Question 31

What is De-excitation?

Answer 31

• Move from higher energy to a lower energy level.
• Emits a photon.

Question 32

How do filament lamps work?

Answer 32

-Current in a filament causes it to heat up, electrons are emitted.
- Electrons are accelerated by a potential difference and collides with electrons in the mercury atom.
- Transfers energy which causes atomic electrons in the mercury atom to excite and de-excite.
- When de-excitation occurs a UV photon is emitted.
- The UV photon absorbed by phosphor electrons and excites it.
Then de-excites it 2 times visable photons are emitted.

Question 33

What is wave-particle duality?

Answer 33

Physical entities can show wave-like or particles like properties.