Particles and Waves

Question 1

Bohr model of the atom – Ionisation level

Answer 1

The energy level an electron is in when it has zero potential energy and can escape from the atom.

Question 2

Fraunhofer lines

Answer 2

Absorption lines in the spectrum of sunlight. These give evidence for the composition of the suns outer atmosphere

Question 3

Absolute refractive index

Answer 3

The ratio of the speed of light in a vacuum to to the speed of light in a medium

Question 4

Irradiance

Answer 4

Power per unit area I=P/A

Question 5

Bosons

Answer 5

These are the force mediating particles. Photons (electromagnetic force), W and Z bosons (weak nuclear force), gluons (strong nuclear force) & Higgs boson

Question 6

Snell’s Law

Answer 6

n = sinθ₁/sinθ₂ = λ₁/λ₂ = v₁/v₂

Question 7

Emission spectrum

Answer 7

Range of frequencies emitted when electrons fall to lower energy levels. Each element has a unique emission spectrum.

Question 8

Point source of light

Answer 8

A source of light coming from a single point and giving off light in all directions e.g. small light bulb or a distant star.
I = k/d2 for a point source. I1 d1^2= I2 d2^2

Question 9

Absorption spectrum

Answer 9

Range of frequencies absorbed when electrons rise to higher energy levels. Each element has a unique absorption spectrum.

Question 10

Interference

Answer 10

This is evidence for the wave model of light

Question 11

Baryons

Answer 11

Hadrons consisting of 3 quarks

Question 12

Orders of magnitude

Answer 12

1x103 is 3 orders of magnitude smaller than 2.4x106

Question 13

Photoelectric effect

Answer 13

This is evidence for the particle model of light. Photons of a sufficient energy can eject electrons from the surface of a material (photoemission).

Question 14

What does E = mc² represent?

Answer 14

In nuclear fission and fusion reactions mass is lost. This lost mass is converted into energy

Question 15

Mesons

Answer 15

Hadrons consisting of quark - anti-quark pairs

Question 16

Nuclear Fusion reactors

Answer 16

Require charged particles at very high temperature (plasma) which have to be contained by magnetic fields

Question 17

Coherent Waves

Answer 17

Waves that have the same frequency and constant phase difference

Question 18

Fermions

Answer 18

These are the matter particles. Consisting of quarks (Six types: up, down, charm, strange, top, bottom) and leptons (electron, muon and tau, together with their neutrinos).

Question 19

Define electric field

Answer 19

A region where a charged particle experiences a force

Question 20

Threshold Frequency

Answer 20

Minimum frequency of a photon required for photon emission

Question 21

Beta decay

Answer 21

This was the first evidence for the neutrino

Question 22

Define voltage (potential difference)

Answer 22

V=W/Q
Work don per coulomb of charge

Question 23

Hadron

Answer 23

Composite particle consisting of quarks.

Question 24

Relationship between refractive index and critical angle

Answer 24

sin θ_c = 1 / n

Question 25

Work Function

Answer 25

Minimum energy of photon required for photon emission

Question 26

Right hand rule for finding the direction of the force on charged particles moving in a magnetic field.

Answer 26

First finger = Direction of magnetic field (N to S) Middle finger = direction of electron current. Thumb = direction of the force on the particle.

Question 27

Refractive index and frequency relationship

Answer 27

Refractive index of a medium increases as the frequency of incident radiation increases.

Question 28

Constructive Interference

Answer 28

Occurs when 2 waves with a phase difference of an integer multiple of wavelengths meet and combine. Path difference =m λ

Question 29

Critical Angle

Answer 29

The angle of incidence when the angle of refraction is equal to 90 degrees.

Question 30

Ek=hf-hfo

Answer 30

Electron kinetic energy=energy of photon - work function

Question 31

Electric field patterns for single point charges.

Answer 31

A positive charged has lines uniformly coming out from a single point with arrows pointing out the way, negative charge lines should be uniformly surrounding the charge with arrows pointing in the way

Question 32

Total internal reflection

Answer 32

This occurs whenever the angle of incidence is greater than the critical angle.

Question 33

Destructive Interference

Answer 33

Occurs when 2 waves with a phase difference of an integer multiple of 1/2 wavelengths meet and combine. Path difference = (m+1/2) λ

Question 34

Diffraction grating formula m λ = d sin θ

Answer 34

``` m = order of maximum λ = wavelength of source d = distance between slits θ = angle from the central (zero order) maximum ```

Question 35

Electric field patterns for pairs of point charges.

Answer 35

If both charges are negative all field lines surrounding will push each other away, If one negative one positive the field lines go from negative to positive

Question 36

Electric field pattern between two charged parallel plates.

Answer 36

Negative charges attract the positives so field lines go towards them

Question 37

Bohr model of the atom - Ground State

Answer 37

The lowest energy level and electron can be in. This corresponds to the level closest to the nucleus.