ch 15.1 - refraction definition: refraction change in speed of light as it moves from one medium to...
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Ch 15.1 - RefractionCh 15.1 - Refraction
Definition: RefractionDefinition: Refraction
Change in speed of light as it moves from one medium to another.
Can cause bending of the light at the interface between media.
Index of RefractionIndex of Refraction
• The ratio of the speed of light in a vacuum to its speed in a given transparent medium
Index of RefractionIndex of Refraction
speed of light in vacuum
speed of light in medium
n = c/v
n =
Snell’s LawSnell’s Law
n1
n2
1
angle of incidence
2
angle of refraction
n1sin 1 = n2sin 2
nn11 < n < n22
n1
n2
1
2
light bends toward normal
nn11 > n > n22
n1n2
1
2
light bends away from normal
HomeworkHomework
• P567 #1-3 (Snell’s Law)
• P567 #1-3 (Section Review)
15.3 – Optical Phenomena15.3 – Optical Phenomena
DispersionDispersion
The separation of white light into colors due to different refractive indices for different wavelengths.
DispersionDispersionDue to different indices of refraction for different wavelengths of light.
Useful DefinitionsUseful Definitions
• Total Internal Reflection – the complete reflection of light at the boundary of two transparent media
• Critical Angle – the minimum angle of incidence for which total internal reflection occurs
Critical Angle of IncidenceCritical Angle of Incidence
n1
n2
c
Light would refract 90o so it reflects instead, undergoing total internal reflection.
r
n1 > n2
Calculating Critical AngleCalculating Critical Angle
n1sin(1) = n2sin(2)
n1sin(1) = n2sin(90o)
n2 = n1sin(c)
Total Internal ReflectionTotal Internal Reflection
n1
n2
i r
Occurs only when angle of incidence > critical angle
HomeworkHomework
• P582 #1-4, p585 #1-3
15.2 – Thin lenses15.2 – Thin lenses
Lens typesLens types
• Converging – can produce real or virtual images
• Diverging – can produce only virtual images
Ray diagramsRay diagrams
• Same rays as we drew for mirrors
• Rays will always go through the mirror (not reflected) but will be somehow bent (refracted)
Useful DefinitionsUseful Definitions
• Lens – a transparent object that refracts light rays, causing them to converge or diverge to create an image.
• **Big difference with mirrors**– Real is on the right side of the lens. Why?
• + side of mirror is ride side
• - side of mirror is left side
Converging lens #1Converging lens #1
C F
Real, Inverted, Reduced Image
F2F 2F
Converging lens #2Converging lens #2
C F
Real, Inverted, True (Same size) Image
F2F 2F
Converging lens #3Converging lens #3
C F
Real, Inverted, Enlarged Image
F2F
Converging lens #4Converging lens #4
C F
Virtual, Upright, Enlarged Image
F
For converging lensesFor converging lenses
• f is positive• p is positive• q is positive for real images and negative for
virtual images• M is negative for real images and positive for
virtual images • hi is negative for real images and positive for
virtual images
Diverging lensDiverging lens
C F
Virtual, Upright, Reduced Image
F
For diverging lensesFor diverging lenses• f is negative• p is positive• q is negative• M is positive and < 1• hi is positive and < ho
HomeworkHomework
• P576 #1-4