Waves And Oscillation 2 Flashcards
Define superposition (1)
-the combination of 2 or more waves to form a resultant wave
State the principle of superposition (2)
-the resultant displacement is the vector sum of the individual displacement due to each other
-when 2 waves are of small or big amplitude, they either cancel out or add up
Define phase (1)
-the measurement of the position of a certain point along the wave cycle
Define standing waves (1)
-a standing waves is the superposition of 2 progressive waves with the same frequency, wavelength p and amplitude in the opposite direction
Define progressive waves (1)
-is a type of wave that Carrie’s energy from one place to another through a medium
Define nodes (1)
Points where the amplitude of the wave is zero
Define anti node (1)
Where the amplitude is maximum
Define monochromatic light (2)
-source of light which have the same frequency and wavelength
-always in phase
State general ideas about the single slit diffraction (3)
-the central fridge is twice as wide as each other the outer fringes
-each of the fringes is the same width
-the outer fringes are less intense than the central fringe
Why is monochromatic coherent sources used in diffraction (3)
-needed to view fringes with different wavelengths or to see young’s fringes clearer
-so you get the same diffraction
-longer wavelengths bend more
Define central maximum (2)
-it is the point with the greatest intensity
-central maximum is the result of waves from all the slits aligning at a certain angle due to constructive interference
Why is the central maximum the brightest (2)
-intensity of light is highest at the centre
-increase in intensity means an increase in number of photons emitted per second
What happens if wavelength increases, state in terms of intensity and diffraction (2)
-increases amount of diffraction
-central maximum is lowered
What happens if slit width increases, state in terms of intensity and diffraction (2)
-decreases amount of diffraction
-intensity of central maximum is higher
What happens if slide width is narrower , state in terms of intensity and diffraction (1)
-makes the fringes wider
State the formula involving angle at which wave forms (1)
n x wavelength = slit spacing x sinO
Define white light (2)
-it is a mixture of different colors
-each having different wavelengths
What is observed when white light is shone through a single slit (2)
-all of the different wavelengths are different by different amounts
-red diffracting the most and it has the greatest wavelength but lowest frequency
What color is the central maximum when white source is used and why (2)
-it’s white
-because it results from the combination of all the colors in the white light spectra
State the formula for fringe spacing (1)
Fringe spacing = ( distance from slit to screen x wavelength ) / spacing between slits
Define and explain constructive interference (5)
-when the wave pulses combine, the resulting pulses have an amplitude equal to the sum of the amplitude of the individual pulses
-Crest + crest gives a bigger crest
-when they are perfectly aligned together they are in phase
- path difference = wave1 - wave2 = whole number of wavelength
-when they’re out of phase path difference is decimals
Define path difference (1)
-distance travelled by the 2 waves from their source to the point where they meet
State and explain the concept of destructive interference (5)
-when 2 or more waves come together and their individual pulses combine in a way that reduces or cancels out their amplitudes
-crest + trough of equal size gives us nothing as 2 displacements cancel out each other
-they are in anitphase
- path difference = wave1 - wave2 = decimal wavelength
-when they’re out of phase the path difference is a whole number
State an application of destructive interference when in phase (2)
-noise canceling earphones
-the headphones cancel out the sound by sending in their own sound by opposite phase which cancels out the noise effect
What happens if the single slit is too wide in two source interference (4)
-it can make the interference pattern less clear
-because the single slit let’s through a lot of light which can weaken the effects of interference
-the dark fringes will become narrower than the bright fringes so contrast is lost
-if the single slit is too wide you might not even see the interference pattern at all
What should you do to get a good interference pattern (1)
-use a single slit that’s narrower or similar in width
How are fringes formed in two source interference (6)
-due to the interference of light from the 2 slits
-when lights from the 2 slits super pose
-lights from the 2 slits is coherent
-bright fringes = constructive interference (in phase)
-dark fringes = destructive interference (out of phase
-central is white fringe
How are bright fringes formed (4)
-where the waves overlap constructively
-when a leak from one wave aligns with the peak of another wave they superpose each other
-the light waves from each slit arrive in phase with each other
-at points where constructive interference occurs , the amplitude of waves add up giving maximum intensity so there is more energy concentrated hence brighter fringe
How are dark fringes formed (3)
-the light from one slit cancels the light from the other slit
-waves overlap in a way that their peaks align with their troughs leading to destructive interference
-and a point of minimum
Define fringe spacing (1)
-the distance from the centre of a bright fringe to the centre of the next bright fringe
What does the equation fringe spacing = (wavelength x distance from slit to screen) / slit spacing tell you ? (3)
-the distance from slit to screen is increased
-the wavelength of the light used is increased
-the slit spacing is reduced
What are the safety precautions needed when using a laser (3)
-wear safety goggles
-never shine a laser towards a person
-don’t shine on reflective surface
What is the law of reflection (2)
-the angle of incidence is equal to the angle of refraction
-when light reflects, a phase change can occur depending on refractive indexes of each medium
When does refraction occur (1)
-it occurs when light passes a boundary between 2 different transparent media
What does refraction occur due to (4)
-different speeds:
Light travels at different speeds in different material
-bending of light:
When light enters s denser material, it slows down and changes direction
What happens when light travels from air to glass (3)
-less dense ti more dense
-light bends towards the normal
-angle of incidence is greater than angle of refraction
What happens when light travels from glass to air (3)
-more dense to less dense
-light bends away from the normal
-angle of refraction greater than angle of incidence
What are the properties that change during refraction (2)
-speed
-wavelength
Define refractive index and state its formula (2)
-it is a property of a material which measures how much light slows down when passing through it
N = speed of light / speed of light in substance
What is the speed of light. (1)
3 x 10^8
What is the refractive index of air (1)
1
State the formula of snells law (1)
N1 x sinOi = N2 x sinOr
When does total internal refraction occur (4)
-angle of incidence is greater than the critical angle
-n1 > n2
-as the angle of incidence increases, the angle of refraction also increases until it gets closer to 90 degree
-when the angle of refraction is exactly 90, light is refracted along the boundary
What are the conditions required for TIR (2)
- n1> n2
-angle of incidence greater than critical angle
State formula for critical angle (1)
Sin 0c = n2 / n1
State the meaning of coherent sources (3)
-same phase difference
-same wavelength
-same frequency
