Transcript Interference & Diffraction of Light

Daily Challenge, 1/7
If light is made of waves and
experiences interference, how will
the constructive and destructive
interference appear to us?
Light shows Interference
Interference is the mutual effect (superposition
principle) of two beams of light resulting in a loss of
intensity in certain regions (destructive interference)
and an increase of intensity of other regions
(constructive interference)
Double Slit Interference – standing wave pattern
similar to water wave tank
Interference in thin films – occurs due to reflection
off front and back of film being slightly out of phase
Young’s Double Slit Experiment
Thin Film Interference
http://sol.sci.uop.edu/~jfalward/lightinterference/lightinterference.html
Diffraction of Light
Diffraction – the spreading of light into a region
beyond an obstruction (happens on the scale of
wavelength)
Diffraction Gratings – optical surfaces with many
parallel, closely spaced grooves
when a beam of monochromatic light is passed
through… a principal image, along with less
intense 1st, 2nd, etc. images, are produced
λ = d (sin θn) / m
λ – wavelength of monochromatic light
d – grating constant, in length units m – order number
θn – diffraction angle, measured from principal image
Daily Challenge, 1/8
Check out the “rainbow glasses”
and “snowflake glasses.”
Consider the physics of light
discussed yesterday.
How do these glasses work?
Daily Challenge, 1/9
Minilab: (15 points)
Use the diffraction gratings of known
spacing to determine the wavelength of
a laser. Sketch your experimental
setup and show your work.
Remember
λ = d (sin θn) / m
λ – wavelength of monochromatic light
d – grating constant, in length units m – order number
θn – diffraction angle, measured from principal image
Physics Daily Challenge, 1/12
The specifications (accepted values)
for groove spacing are 1.6 μm/groove
on a CD and 0.7 μm/groove on a DVD.
If you use a laser of known wavelength
and the diffracted reflection images of
the laser beam to calculate a groove
spacing of 15,300 Å for a CD,
what is the absolute and relative
error of your measurement?