Transcript Ch 15.1 - Refraction

Ch 15.1 - Refraction
Definition: 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 Refraction
• The ratio of the speed of light in a
vacuum to its speed in a given
transparent medium
Index of Refraction
n=
speed of light in vacuum
speed of light in medium
n = c/v
Snell’s Law
angle of incidence
n1
n2
1
n1sin 1 = n2sin 2
2
angle of refraction
n1 < n2
light bends toward normal
n1
n2
1
2
n1 > n2
n1
n2
1
light bends away from
normal
2
Homework
• P567 #1-3 (Snell’s Law)
• P567 #1-3 (Section Review)
15.3 – Optical Phenomena
Dispersion
The separation of white light into colors
due to different refractive indices for
different wavelengths.
Dispersion
Due to different indices of
refraction for different
wavelengths of light.
Useful 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 Incidence
c
Light would refract
90o so it reflects
instead, undergoing
total internal
reflection.
n1
r
n2
n1 > n2
Calculating Critical Angle
n1sin(1) = n2sin(2)
o
n1sin(1) = n2sin(90 )
n2 = n1sin(c)
Total Internal Reflection
i
r
Occurs only when
angle of incidence >
critical angle
n1
n2
Homework
• P582 #1-4, p585 #1-3
15.2 – Thin lenses
Lens types
• Converging – can produce real or virtual
images
• Diverging – can produce only virtual
images
Ray diagrams
• Same rays as we drew for mirrors
• Rays will always go through the mirror (not
reflected) but will be somehow bent
(refracted)
Useful 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 #1
2F
Real,
Inverted,
Reduced
Image
F
C
F
2F
Converging lens #2
2F
Real,
Inverted,
True (Same
size) Image
F
C
F
2F
Converging lens #3
2F
Real,
Inverted,
Enlarged
Image
F
C
F
Converging lens #4
F
Virtual,
Upright,
Enlarged
Image
C
F
For 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 lens
F
Virtual,
Upright,
Reduced
Image
C
F
For diverging lenses
• f is negative
• p is positive
• q is negative
• M is positive and < 1
• hi is positive and < ho
Homework
• P576 #1-4