OPTICS + PARTICLE STUFF

Question 1

What is the visible light section of spectrum?

Answer 1

380nm - 750nm

Question 2

What are the two parts of optics?

Answer 2

Geometric (for objects larger than wavelength, propagation is through geometrical objects)
Wave optics (for objects around size of wavelength)

Question 3

What does Huygen’s principle state?

Answer 3

Every point on a wavefront may be considered as a source of a secondary wave that spreads out in the forward direction at speed equal to the speed of the wave.

Question 4

What is the law of reflection?

Answer 4

Angle of incident ray is equal to angle of reflected ray

Question 5

What are the refraction angles for n2> n1 and n1 > n2

Answer 5

For n2 > n1, a > b

For n1 > n2, b > a

Question 6

When does total internal reflection occur?

Answer 6

When the incidence angle of ray a is greater than the critical angle (critical angle - angle at which ray will travel along 90 degrees) when trying to travel from a slower medium to a faster medium

Question 7

Why does dispersion of light occur?

Answer 7

As different colours have slightly different index’s of refraction as index of refraction is a function of wavelength

Question 8

What does the double-slit experiment exihibit

Answer 8

The diffraction of light

Question 9

What does wave optics apply to?

Answer 9

Objects that have dimensions similar to wavelengths

Question 10

What is thin film interference?

Answer 10

When a ray reaches a medium some of it reflects and some passes through the next medium boundary. At this boundary the ray reflects in the same manner as the first.

Question 11

What possible phase shifts will occur in thin film interference?

Answer 11

If n2 > n1 then there is a pi phase shift (or wavelength/2) if n1 > n2 then no phase shift will occur.

Question 12

What is polarised light and what occurs in non-polarised light?

Answer 12

Light that vibrates in only one place. Transverse waves can be polarised. In non-polarised light the direction of the electric field changes.

Question 13

What are methods to polarise light?

Answer 13

By a polariser filter (only allows light through in one plane, typically vertical) or reflection.

Question 14

What does Brewsters law convey?

Answer 14

Polarising angle for reflection with reference to the considered mediums.

Question 15

What is particle nature of EM radiation?

Answer 15

The dualism of light - ability of em radiation to behave like a wave or a particle

Question 16

What is quantised energy?

Answer 16

Energy is not continuous but is made up of discrete values (quantised)

Question 17

What is a photon and its relation to photoelectric effect?

Answer 17

A particle of light.

An electron is ejected when a singular photon of sufficient energy strikes it.

Question 18

How is energy and momentum of photon described?

Answer 18

E = hf (energy of photon is quantised)
p = mc = h/wavelength

Question 19

How is moving mass of a photon described?

Answer 19

E = hf =mc^2

==> m =hf/c^2 = h/(c.wavelength)

Question 20

What is a black body?

Answer 20

An object that emits EM radiation of all wavelengths

Question 21

What does Wein’s displacement law explain?

Answer 21

It explains black bodies peak wavelength relationship to temperature (objects emitt wavelength at their highest intensity)

Question 22

What is compton scattering?

Answer 22

When a high energy photon collides with an electron. The scattered photon has a longer wavelength than the incident photon (wavelength change is proportional to scatter angle)

Question 23

What is Braggs law and what does it use/how?

Answer 23

Allows to calculate distance between layers of atoms using x-ray diffraction. 1st x-ray hits an atom, 2nd x-ray comes at the same angle and strikes the atom below 1st. Braggs law: 2dsina = n(wavelength_max)

Question 24

What is the Thomson model of an atom?

Answer 24

Electrons submerged in continuous positive matter

Question 25

What is the Planetary model and which experiment discovered it?

Answer 25

The Rutherford experiment shot alpha particles to a thin gold foil and some alpha particles were scattered back at angles (experiment predicted alpha particles would pass easily). Result meant a small concentrated nucleus and electrons orbit this nucleus.

Question 26

What is the Bohr Model?

Answer 26

It is a quantum mechanical model of a hydrogen atom. Potential energy of an electron in a hydrogen atom is also quantised. Electron can only occupy certain energy levels at specific distances from nucleus.

Question 27

Which series will eject photons in visible light spectrum?

Answer 27

Balmer series

Question 28

What are the 5 different series and their electron level transitions?

Answer 28

Lyman series (n to 1)
Balmer series (n to 2)
Paschen series (n to 3)
Brackett series (n to 4)
Pfund series (n to 5)