Module 4 Part 2- Waves and Quantum Physics

Question 1

What is the difference between a transverse and a longitudinal wave

Answer 1

Transverse waves oscillate at 90° to the direction of energy transfer whereas longitudinal oscillations are parallel to the direction of energy transfer.
Transverse waves can travel through a vacuum but longitudinal waves need a medium to travel through

Question 2

Transverse waves have peaks and troughs whereas longitudinal waves have

Answer 2

Compressions and rarefactions

Question 3

What is amplitude

Answer 3

Amplitude is the distance from the peak/trough to the equilibrium position

Question 4

What is wavelength

Answer 4

Wavelength is the distance from one peak/trough to the next

Question 5

Define period of oscillation (time period)

Answer 5

The time a wave takes to complete one full oscillation

Question 6

Define frequency

Answer 6

The number of wavelengths that pass a given point per second-inverse to time period

Question 7

What is phase difference and what is it measured in

Answer 7

Phase difference is the difference between the displacements of two particles along a wave
or the displacements of two waves-this is measured in degrees° or radians where a circle is a full oscillation

Question 8

What is it called when two particles reach their peak at the same time

Answer 8

In phase

Question 9

What is it called when one particle hits its peak while the other hits its trough

Answer 9

Antiphase

Question 10

What is reflection

Answer 10

Reflection is when a wave changes direction at the border between two mediums therefore remaining in the original medium-wavelength and frequency remain the same

Question 11

What is the law of reflection

Answer 11

Angle of incidence=angle of reflection

Question 12

What is refraction

Answer 12

Refraction is when a wave changes direction towards/away from the normal as it enters a new medium due to a change in speed which occurs when entering a more/less dense medium

Question 13

What is the photoelectric effect

Answer 13

The photoelectric effect is when photons of electromagnetic radiation are shone onto a metal and photoelectrons are emitted off the surface

Question 14

What are the conditions that need to be in place for the photoelectric effect to take place

Answer 14

Incident radiations frequency must be above threshold frequency of the metal-f0

Question 15

What is the name given to the minimum amount of energy to free an electron

Answer 15

Work function-different for each metal

Question 16

What is the equation that links energy, Planck constant and frequency

Answer 16

Energy = h x f

Question 17

What happens to the spare energy after the photoelectric effect occurs

Answer 17

A certain amount of energy is used to overcome the work function, the rest is then transferred into to the kinetic energy of the electron

Question 18

What is the idea of wave-particle duality

Answer 18

It is a theory that de broglie proposed which states that all matter has both wave and particle properties

Question 19

What is the de broglie equation

Answer 19

(De broglie) Wavelength = Planck constant / momentum

Question 20

What is superposition

Answer 20

Superposition is when two waves meet and experience either constructive or destructive interference

Question 21

What is constructive interference

Answer 21

Constructive interference is when the amplitudes of the two waves interfering add to one another to create a larger total amplitude

Question 22

What is destructive interference

Answer 22

Destructive interference is when two waves meet and have opposing amplitudes (one up one down) and the amplitudes subtract from one another giving a smaller total amplitude

Question 23

What is path difference and what is it measured in

Answer 23

Path difference is the distance between a point on a diffracted wave and the source of that diffraction
it is measured in λ which is the wavelength of the wave

Question 24

What is phase difference

Answer 24

Phase difference is the difference between two waves in the cycle of the wavelength and it is measured in degrees or radians-1 wavelength = 360° or 2pi radians

Question 25

What is the equation for the young double slit experiment

Answer 25

Wavelength= slit separation (a) x fringe distance (x) / distance from the slits (D)

Question 26

What is a standing (stationary) wave

Answer 26

A standing wave is when two progressive waves superimpose oppositely and form a wave which doesn’t transfer any energy and has nodes and anti-nodes

Question 27

What is diffraction

Answer 27

Diffraction is a phenomenon unique to waves and it is when the wave is spread out after passing through a gap the same size as its wavelength-wave speed, wavelength and frequency are not altered

Question 28

What is polarisation

Answer 28

Polarisation is unique to transverse waves and it is when a wave is confined to a single plane meaning that it only oscillates on one plane (up and down) rather than many

Question 29

What is the intensity of a wave

Answer 29

The intensity of a wave is defined as the power passing through a surface per unit area and in any progressive wave the intensity decreases as distance from the source increases

Question 30

What is the equation for intensity

Answer 30

I = Power / Area

Question 31

What is the order of the electro magnetic waves (biggest to smallest)

Answer 31

Radio waves, micro waves, infra red, visible light, ultraviolet, x rays, gamma rays

Question 32

What is refractive index and what is the equation for it

Answer 32

Refractive index is the level to which a material refracts a wave when it passes through it Equation: refractive index (n)= speed of light in a vacuum (c) / speed of light in the material (v)

Question 33

What is total internal reflection and what are the conditions for it

Answer 33

Total internal reflection is when all of the light on the incident boundary is reflected back into the original medium It happens when: -the original material has a higher refractive index -the angle of incidence is higher than the critical angle

Question 34

What are the two equations for energy of a photon

Answer 34

E=hf E=hc / lambda

Question 35

What fact supports the particulate nature of a photon

Answer 35

When the photoelectric effect occurs, the emission happens instantly rather than taking time as the wave theory suggests

Question 36

What is the equation that links energy, planck constant, speed of light and wavelength

Answer 36

E=hc/ lambda

Question 37

What is the Planck constant

Answer 37

6.63x10^-34

Question 38

How many joules is one electron volt

Answer 38

1eV=1.6x10^-19 J

Question 39

What is Einsteins photoelectric effect equation

Answer 39

E (energy) = φ (work function) + KE max

Question 40

What is a piece of evidence for the wave behaviour of an electron

Answer 40

Electron gets diffracted when passed through a graphite film

Question 41

What is fundamental frequency

Answer 41

Minimum frequency of a stationary wave possible on an instrument (double length of string) It is dependent on the length, diameter, density and tension (if it’s on a string)

Question 42

What does coherent mean

Answer 42

When two waves have both -same frequency -same phase difference

Question 43

What is the relationship between the refractive index of a material and the angle between the wave and the normal

Answer 43

n is inversely proportional to sin θ

Question 44

What is the relationship between path difference and phase difference

Answer 44

Phase difference is double path difference (for coherent waves)

Question 45

What is a node

Answer 45

A node is a point in a stationary wave of zero displacement

Question 46

What is an anti-node

Answer 46

An anti-node is a point in a stationary wave with maximum displacement