5.7 Diffraction Grating Flashcards
what is a diffraction grating
a plate with many closely spaced parallel slits ruled on it
what happens when a parallel beam of monochromatic light is directed normally at the diffraction grating
light is transmitted by the grating in certain directions only
why is light transmitted by diffraction grating only transmitted in certain directions
the light passing through each slit is diffracted
the diffracted light waves from adjacent slits reinforce each other in certain directions only including the incident light direction and cancel out all other directions
what is the central beam referred to as
the zero order beam
what direction is the zero order beam
the same direction as the incident beam
when will the angle of diffraction between each transmitted beam and the central beam increase
if light with a longer wavelength is used
grating with closers slits are used
how do the diffracted wave fronts reinforce each other
a diffracted wave front emerges from each slit and reinforces with another slit adjacent to it often by reinforcing with the wavefront from an adjacent slit that was emitted one cycle earlier forming a new wavefront
what is the perpendicular distance from a slit to its new formed wavefront
n lambda
diffraction grating equation
d sin theta = n lambda
d = grating spacing
how do you find the number of slits per metre on the grating
n = 1/d
d= is the gating spacing
the smaller the value of d the larger the angle of diffraction therefore
the larger the number of of slits per metre the bigger the angle of diffraction
what does 1 degree equal in minutes
60’
how do you find the maximum number of orders produced
substitute sin 90 into the grating equation
answer has to be rounded down to the nearest whole number
what produces a continues spectra
a filament lamp
what is a continuous spectra
continuous spectra of colour from deep violet at 350 nm to deep red at 650nm
what does the most intense part of a contiumos spectra depend on
the temperature of the light source
the hotter the light source the shorter the wavelength of the brighetset part of the spectrum
what makes a line emission spectra
glowing gas in a vapour lamp or discharge tube
how does a line emission spectra work
emits light at specific wavelengths so its spectrum consists of narrow vertical lines of different colours
what do the different lines mean in a emission spectra
the wavelengths of the lines are characteristics of the chemical element that produced the light
If a glowing gas contains more than one element the elements in the gas can be identified by observing its line spectrum
what is a line absorption spectra
a continuous spectrum with narrow dark lines at certain wavelengths
the pattern in the dark lines is due to the elements in the glowing gas
these elements absorb light of the same wavelengths that they emits so the transmitted light is missing these wavelengths
