Waves

Question 1

Things that are particle like behaviour

Answer 1

• having/ transferring kinetic energy
• having/ transferring momentum
• affected by forces such as gravity or electrostatic

Question 2

Things that are wave- like behaviour

Answer 2

• reflection
• refraction
• polarisation
• Diffraction
• interference

Question 3

De Broglie wavelength equation

Answer 3

Wavelength = plank constant / the particles momentum

Question 4

Momentum =

Answer 4

Mass x Velocity

Question 5

What do particles with more momentum and kinetic energy have?

Answer 5

They have a smaller wavelength

Question 6

How can we see particles acting like a wave?

Answer 6

By observing them diffract while passing between gaps in atoms of graphite

Question 7

What is an interference pattern?

Answer 7

• Where diffracted waves overlap when passing through 2 or more slits.
• where the waves arrive in phase, they add up, and this is seen as areas of brighter light and vice verca for areas where waves are out of phase/ darker because they cancel each other out.
• we call the patterns of bright spots/lines ‘fringes’

Question 8

When does light give clearer interference patterns?

Answer 8

When the gaps it passes through are the same size as the wavelength

Question 9

How can we see the de broglie equation in action?

Answer 9

Using an electron gun in an evacuated tube

Question 10

When are standing waves formed?

Answer 10

• when waves are trapped, if their wavelengths ‘suit’ the space.
  -this is because wavelengths interfere and constantly add up in some spaces (anti-nodes) and cancel out in other spaces (nodes)
  -e.g musical instruments with a vibrating string

Question 11

When can electrons orbit?

Answer 11

in patterns where their orbital circumference is equal to a whole number of their de-broglie wavelengths, so they can only orbit with certain velocities and certain energies.

Question 12

Change in energy of an atom when it is de-excited from energy level n1 to n2 equation.

Answer 12

Question 13

What does it mean when a transverse wave is plane-polarised?

Answer 13

When the vibrations stay in one plane only

Question 14

Sketch a rope model and diagram to show polarisation

Answer 14

Question 15

What is the cycle of a wave

Answer 15

One complete cycle of a wave is from maximum displacement to the next maximum displacement

Question 16

What is the phase of a vibrating particle

Answer 16

– The phase of a vibrating particle at a certain time is the fraction of a cycle it has completed since the start of the cycle
– the phase difference between particles vibrating at the same frequency is the fraction of a cycle between the vibrations of the two particles, measured either in degrees or radians
– one cycle = 360° = two pi radians

Question 17

Node def

Answer 17

Point at which the wave has no displacement

Question 18

Antinode def

Answer 18

Maximum amplitude

Question 19

What is pitch of a sound wave correlated to

Answer 19

Frequency

Question 20

First harmonic frequency

Answer 20

F= c/2L

Question 21

Second harmonic frequency

Answer 21

F=c/2L

Question 22

Third harmonic frequency

Answer 22

F= 3C/2L

Question 23

Why can only transverse waves be polarised

Answer 23

• in transverse waves the vibrations take place perpendicular to the direction of energy transfer • in longitudinal waves the vibrations take place in the same direction as the energy transfer
• polarisation restricts the vibrations to one plane by absorbing the vibrations at right angles to this plane
• longitudinal waves cannot be polarised because the vibrations have to take place for energy to be transmitted

Question 24

What is a coherent light source

Answer 24

A light source which emits light waves with a constant phase difference and frequency

Question 25

What are the three types of spectra in diffraction gratings

Answer 25

Question 26

Frequency vs time period

Answer 26

Frequency refers to how often something happens. Period refers to the time it takes something to happen.

Question 27

What is phase difference

Answer 27

Phase difference tells us how far apart the waves are when comparing their phases (you can think of this as their peaks and troughs).

Question 28

Which electromagnetic waves have the shortest wavelengths

Answer 28

Question 29

What do the different components of the fringe spacing equation mean?

Answer 29

Question 30

Coherent wave source def

Answer 30

A source that produces waves with a constant phase difference but same wavelength