MicroscopyPioneers
Figure 1.
obvious that the refractive index of an unknown specimen can be determined by the Brewster angle. Tis feature is particularly useful in the case of opaque materials that have high absorption coefficients for transmitted light, rendering the usual Snell’s law formula inapplicable. Determining the amount of polarization through reflection techniques also eases the search for the polarizing axis of a sheet of polarizing film that is not marked.
Te principle behind Brewster’s angle is illustrated Fig-
ure 1 for a single ray of light reflecting from the flat surface of a transparent medium having a higher refractive index than air. Te incident ray is drawn with only two electric vector vibration planes but is intended to represent light having vibrations in all planes perpendicular to the direction of propagation. When the beam arrives on the surface at a critical angle (Brewster’s angle, represented by the variable θ in Fig- ure 1), the polarization degree of the reflected beam is 100 percent, with the orientation of the electric vectors lying perpendicular to the plane of incidence and parallel to the
reflected surface. Te incidence plane is defined by the incident, refracted, and reflected waves. Te refracted ray is oriented at a 90-degree angle from the reflected ray and is only partially polarized. For water (refractive index of 1.333), glass (refractive
index of 1.515), and diamond (refractive index of 2.417), the critical (Brewster) angles are 53, 57, and 67.5 degrees, respectively. Light reflected from a highway surface at the Brewster angle oſten produces annoying and distracting glare, which can be demonstrated quite easily by viewing the distant part of a highway or the surface of a swimming pool on a hot, sunny day. Modern lasers commonly take advantage of Brewster’s angle to produce linearly polarized light from reflections at the mirrored surfaces positioned near the ends of the laser cavity.
Interactive Java Tutorial
http://micro.magnet.fsu.edu/primer/java/polarizedlight/
brewster/
index.html Brewster’s Angle Demo. A common source of polarized
light is that reflected from a dielectric medium such as a window pane, sheet of paper, or a highway on a sunny day. Tis tutorial demonstrates the polarization effect on light reflected at a specific angle (the Brewster angle) from a transparent medium. Adjustable parameters include the incident beam wavelength, refractive index of the dielectric medium, and the rotation angle from which the tutorial is viewed by the visitor.
lumencor
®
when you can have a light engine? a powerful, white-light, solid-state iluminator
why buy a lamp SOLA light engineTM
Solid State Sources, the Power of an Arc Lamp and Powerful, stable white light Minimal heat generation Illumination uniformity Short warm-up time Millisecond switching times Long life > 15,000 usable hours Off-the-shelf configurations
Use with any microscopy software in the marketplace Couples to all major brands of microscope via 3mm LLG Integrates with existing filter cubes and hardware configurations
48
Lumencor, Inc 14964 NW Greenbrier Parkway, Beaverton, OR 97006 USA T 503-213-4269
www.lumencor.com www.microscopy-today.com • 2011 November
specific outputs are a function of instrument parameters - results will vary
SOLA light engine 175W Xenon lamp 120W Metal Halide lamp
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76