Snell’s Law Snell’s Law describes refraction as light strikes the boundary between two media n 1 sin q 1 = n 2 sin q 2 The index of refraction of a pure vacuum and of air is n = 1. The index of refraction of every other substance is greater than 1. incidence refle cted refracted q q q
incidence. q. q. reflected. refracted. q. Snell’s Law. Snell’s Law describes refraction as light strikes the boundary between two media n 1 sin q 1 = n 2 sin q 2 The index of refraction of a pure vacuum and of air is n = 1 . - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Snell’s LawSnell’s Law describes refraction as
light strikes the boundary between two media
n1 sin q1 = n2 sin q2
The index of refraction of a pure vacuum and of air is n = 1.
The index of refraction of every other substance is greater than 1.
At some Critical Angle of incidence, the angle of refraction is 90°.
Beyond that critical angle, no light that is refracted!
All of the light is reflected back into the original medium.
This is called Total Internal Reflection
inciden
ce
reflected
qcritical
1
2critical n
nsin q
n1
n2
)190(sinsinsin 2211 qq nn
The most useful application of the phenomenon of
Total Internal Reflection is in
Fiber Optics
When wavefronts pass through a narrow slit they spread out. This effect is called diffraction.
The amount of diffraction depends upon the size of the slit. If the slit is comparable in size to the wavelength of the wave then maximum diffraction occurs.
If the wavelength of light is longer, the pattern on the screen is more spread out.
(700 nm- 400 nm) Red light spreads out more than violet.If the screen is farther, the pattern on the screen is more spread out.If the slits are CLOSER to each other, the pattern on the screen is more spread out.
Optical diffraction effects can be seen with eye - in fact most of us when children have noticed it, but ignored it
when becoming adults.
Look through a narrow slit between your fingers. If you look carefully you should see the objects behind are distorted and that blackish bands parallel to the slit
appear in the gap. The bands are diffraction patterns.
• In the atmosphere, diffracted light is actually bent around atmospheric particles -- most commonly, the atmospheric particles are tiny water droplets found in clouds.
• An optical effect that results from the diffraction of light is the silver lining sometimes found around the edges of clouds
ml = d(x ÷ L) = dsinqm- “order” (m = 0 is the central bright spot)l- wavelength of lightd- distance between the slitsx- distance from central bright spot to another
bright fringeL- distance from the slits to the screenq- the angle between the line to the central bright
spot and the observed bright fringe.
Different frequencies (colors) of lightdiffract by different amounts
• The more slits there are, the narrower the fringes become.
• The fringes on top are from two slits.• The fringes on bottom are from eight slits.• A “diffraction grating” has hundreds of slits per