5. Waves Flashcards

Question

What happens with energy in a stationary wave?

Answer 1

The energy is stored in the wave, as no energy is transferred anywhere

Answer 2

On a stationary wave, a node is where there is no vibration and no movement

Answer 3

On a stationary wave, an anti-node is where there is vibration and max amplitude

Answer 4

They do not move along the string The only movement is from the by anti-nodes, up and down The waves are in anti phase at the nodes and anti-nodes

Answer 5

The first standing wave we can produce The smallest wave in terms of λ we can make half a wavelength Called the first harmonic

Answer 6

A harmonic is the multiple of a fundamental wave E.g a full wave is the 2nd harmonic

Answer 7

The amount of energy passing through a wave per second and unit area is the intensity of the wave As P=E/t I=P/A Where A=area(m^2) I is in (Wm^-2)

Answer 8

c=3x10^8ms^-1

Answer 9

EM waves are made out 2 different types of waves: - electric field - magnetic field They are perpendicular to each other They have no plane - they move in all directions everywhere, when unpolarised

Answer 10

The spreading out of waves after passing through a gap or passing around an obstacle Huygen's principle proves this

Answer 11

The amount of diffraction depends on the ratio between the wavelength, λ and the gap, b The closer λ is to b, the more diffraction sinθ=λ/b

Answer 12

Every point on a wavefront is a new secondary source of circular waves So the waves superpose to make a new wavefront

Answer 13

Waves superpose in a pattern after passing through the slits. They hit the screen, superposing constructively and destructively This creates a pattern, with the biggest constuctive interference in the centre (central maximum) then gradually goes out and gets smaller and fades called first order, then second etc...

Answer 14

dsinθ=nλ d= distance between the slits (like b) n= number of order This is because the closer the wavelength to the size of gaps, d the more diffraction

Answer 15

The more slits, the sharper and more defined the lines are But they all make the same pattern

Answer 16

Red light has a longer λ than violet - so the λ is closer to the slit size, so red diffracts more - also can superpose for a longer distance Makes red's central maximum and orders longer

Answer 17

They behave like light and have wave like properties Electrons can also diffract

Answer 18

We can diffract the electrons using this experiment - There is a 6V charge going through the wire - The wire heats up and emits electrons - They just hover around, but are instead accelerated towards the anode (+ve) at 6000V - There is a small hole in the anode, made of graphite, so the electrons go through that and they diffract - Through the crystalline structure - acting as slits - The electrons are going too fast to stop, so they hit the fluorescent screen, making a diffraction pattern

Answer 19

h is a constant relating energy of a photon to it's frequency E=hf h = 6.63x10^-34 Js So where E = the energy of 1 photon And f = the frequency of the wave

Answer 20

A photon is a massless 'quantum' (packet) of EM energy Made up of all forms of EM radiation Shows that energy is transferred through small packets as photons

Answer 21

de Broglie discovered very small, fast moving particles, like electrons can behave as waves - called matter waves He relates momentum, p to their wavelength λ =h/p where p=momentum As p=mv λ =h/mv

Answer 22

≈1x10^-13

Answer 23

≈1x10^-11

Answer 24

≈1x10^-8

Answer 25

≈1x10^-7

Answer 26

≈1x10^-5

Answer 27

≈1x10^-2

Answer 28

≈1x10 - x10^3

Answer 29

v=√(T/μ) where T=tension in string (N) and μ=mass per unit length of the string (kg m^–1)

Answer 30

Wave refraction In deep water, waves travel faster. As the shore appears, the water becomes more shallow, increasing friction of waves, refracting the waves and banding their pathway to face the shore