2.5 INTERFERENCE AND DIFFRACTION Flashcards
Two points on a wave that are vibrating in exactly** same** way, at the same time
are said to be in phase
two crests, two troughs
Two points that are vibrating, in exactly opposite way,
at the same time, are said to be exactly/180deg out of the phase
crest and trough
Coherent sources
are two sources if they are oscillating (коливальний) with** a constant phase relationship/difference**
same frequency, wavelength and speed
Interference
is the test for a wave/ provides evidence for the wave nature of light
Interference pattern
observed when coherent waves overlap
Constructive interference
when 2 waves of equal amplitude meet** in phase**, they combine to form wave of twice the amplitude
**Destructive interference **
when 2 waves of equal amplitude meet out of phase, they combine the form a wave of zero amplitude(line)
Interference fringes
a series of bright and dark bands corrensponding to regions of constructive and destructive interference reapectively
The diffrence in distance travelled by waves from different coherent sources
is PATH DIFFERENCE
MAXIMA IS
a point of constructive interference, formular
Path difference=mL
MINIMA IS
A point of destructive interference, formular Path difference=(1/2+m)L
where m is oder number
Young’s Double Slit Experiment
x=LD/d
x is m, L is path diffrence, D is distance between screen and slits
d is distance between slits
Grating consists of
many equally spaced slits placed very close together
light diffracts through each slit
its fringers produced are brighter and sharper (comparing to the double slit)
mL=dsinA
fringe spacing(between slits)
can be increased by increasing the wavelenght or decreasing the slit seperation
Grating and White light
Center is zero, white light
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