IB Physics Resolution flippingphysics slideshow for HL Wave Phenomena section; also SL Sight and Waves option.

1. presents
a production
Resolution
1

2. Circular aperture
Light diffracted by a circular aperture forms a pattern
of concentric rings with a bright ‘Airy disc’ in the
centre. Examples of circular apertures are the pupil of
the eye; a camera lens; a radio telescope dish.
Image: livjm.ac.uk

3. Diffraction patterms
Diffraction by circular
Diffraction by slit of width b aperture of diameter b
Average diameter
In both cases, angle is of circle = b/1.22
proportional to wavelength and
inversely proportional to slit
width.
Image: photoresearchers Image: oberlin

4. Resolution
Light passing through an aperture is diffracted. If
the images of two objects viewed through the
aperture are so close that their diffraction
patterns overlap, they will be difficult to resolve.
Resolution is the ability
to distinguish two
separate images.
These illuminated objects
can be resolved because
their Airy discs are separate.
Image: NHMFL

5. Rayleigh criterion Image: NHMFL
The limit of resolvability is
when the middle of the
central maximum of one
image coincides with the
first minimum of the
other. At this limit, the
angle subtended by the
two points is given by:
where b is the diameter of
the aperture through which
The Rayleigh criterion the objects are viewed.

6. Better resolution
Better resolution means that
the angle is as small as possible.
This is achieved by using a large
aperture or a short wavelength.
Thus, big lenses resolve better than
small ones and the eye can resolve
violet light better than red because
there is less diffraction at the aperture.

7. Resolution problems
A light telescope has a circular mirror of radius 127 cm.
What is the smallest angle it can resolve for light of
wavelength 550 nm? [264 nrad]
Two stars are 20 ly distant and can just be resolved using
a telescope with aperture of 55 cm. How far apart are
the stars? Assume light of wavelength 450 nm.
[11.5 light-minutes]
Two spotlights are 12 m apart. How far away can a
human eye (pupil diameter 0.40 cm) distinguish the
spotlights if the wavelength of the light is 620 nm?
[63 km]

8. Resolution examples
CDs and DVDs use reflection of laser light from ‘pits’ on
the surface. To store more information, the pits must be
smaller, but there is a limit to resolvability. One solution
is to use shorter wavelength light.
If the object is too small, a light microscope cannot
resolve it due to diffraction at the lens; below uv
(400nm) the light as not visible. An electron microscope
uses electrons with wavelengths of 0.2 nm.
Radio telescopes detect radio waves from space. Since
these have a long wavelength, and are hard to resolve,
the radius of the dishes of the telescopes is huge.

9. Where these two gold
crystals meet they are
joined by a complex
arrangement of atoms,
forming a nano-bridge.
The atoms are 2.3
angstroms apart. This Image from Hubble
resolution is possible Space Telescope of
due to electron binary star system just
microscopy. resolved. It is 8 000 ly
away and a third
unresolved star is
suspected.

10. a production
MUCH MORE AT
http://nothingnerdy.wikispaces.com
http://nothingnerdy.wikispaces.com/11.4+Resolution
10