AS Mock Flashcards KC
What are progressive waves?
Wave that transfers energy from one point to another without transferring the medium itself
What are examples of progressive waves
Transverse
Longitudinal
What are longitudinal waves?
the particles oscillate parallel to the direction of the wave travel (and energy transfer) Longitudinal waves show areas of compressions and rarefactions.
What are some examples of longitudinal waves?
Sound waves
Ultrasound waves
P waves
What are transverse waves?
where the particles oscillate perpendicular to the direction of the wave travel (and energy transfer)
What are some examples of transverse waves?
ripples on the surface of water.
vibrations in a guitar string.
a Mexican wave in a sports stadium.
electromagnetic waves – eg light waves, microwaves, radio waves.
seismic S-waves.
Which types of waves polarise?
Transverse waves only
What is the relationship between amplitude and intensity?
A^2 directly proportional to I
A=A0 X COS THETA
A = amplitude of light coming through
A0 = amplitude of light that came through the first filter
What is Malus’ law?
I=I0 X cos^2 theta
When does interference occur?
When waves overlap and their resultant displacement is the sum of the displacement of each wave
This result is based on the principle of superposition
When are waves coherent?
Same frequency
Constant phase difference
What is coherence?
Points where the 2 waves are in phases, the resultant amplitude is somewhere in between the two extremes
When coherent sound waves are in phase, the sound is larger due to constructive interference
Why is coherence important?
Coherence is important in order to produce an observable, or hearable interference pattern
What is an example of coherent light source
Laser light
What is an example of an incoherent source?
Filament lamp
What is constructive interference?
Constructive interference occurs when the maxima of two waves add together (the two waves are in phase), so that the amplitude of the resulting wave is equal to the sum of the individual amplitudes.
when two waves overlap in such a way that they combine to create a larger wave
What is destructive interference?
happens when two waves overlap in such a way that they cancel each other out
What is path difference?
difference in distance travelled by 2 waves from their sources to the point where they meet
What is the condition for constructive interference?
path difference of n lambda (in phase)
What is the condition for deconstructive interference?
path difference of (n+1/2) lambda (out of phase)
Refractive index equation
n = c/v
c = speed of light in a vacuum
V = speed of light in a material
When does refraction occur?
When a wave passes from one transparent medium to another
What two things happen when refraction occurs?
Speed of wave changes
Wave will change direction
What is snell’s law?
n1 x sin theta1 = n2 x sin theta2
n1 = refractive index
the higher the refractive index, the slower the EM radiation travels through this material compared with its speed in a vacuum
What is the critical angle?
Is the angle of incidence in a dense medium such that the angle of refraction in the less dense medium is = 90 degrees
What is total internal reflection?
Initially, at an angle smaller than the critical angle, refraction will occur but there will also be a weak reflected ray.
When angle of incidence increases, angle of refraction increases so reflected ray gets stronger
At an angle of incidence greater than the critical angle, no refraction occurs and all of the light will be reflected - TOTAL INTERNAL REFLECTION
Critical angle equation
Sin C = n2/n1
READ POLARISING AND YOUNG DOUBLE SLIT PAGES
What is the benefit of increasing the no of slits
Increases the brightness and sharpness of the maxima and makes it easier to measure an accurate value for the wavelength of light
Maxima are further apart so the angle can be measured with a lower % uncertainty
For constructive interference to occur and for a maximum to be produced on the screen there must be a whole no of wavelengths and they must occupy a distance of d sin theta
n lambda = d sin theta
n = order of maximum (order - no of the pattern on either side of the central maximum)
d = separation of the slits
theta = angle that the beam makes with the grating
lambda - wavelength of the incident monochromatic wave
READ STANDING WAVES PAGES
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Kirchhoff’s 1st law
sum of the current entering a junction in a circuit is = to the sum of the currents leaving the junction
conservation of charge
Kirchhoff’s 2nd law
In any closed loop, the sum of the emf is = to the sum of the product of the current and the resistance
conservation of energy
Potential divider derivation
How does LDR work?
When intensity of light increases, the resistance decreases
