PHY 2054C – College Physics B
Fall 2004
Electricity, Magnetism, Light
Optics and Modern Physics
Dr. Ingo Wiedenhöver
Dr. A. Volya
Today:
1) Geometric Optics
2) Focussing Mirrors
3) Refraction and Total Internal Reflection
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Geometric Optics-College Physics B-Lecture 10 Slides-Physics, Slides of Physics
If light passes from a “thinner” to a “denser” medium, (n2>n1) it is refracted toward the normal. Geometric Optics, Focussing Mirrors, Refraction, Total Internal Reflection, Wavelength, Frequency, Properties, Optics, Mirror Images, Focussing Light, Concave Mirror, Mirror Equations, Index of Refraction, Refrective Index, Snell's Law, Dr A Volya
Typology: Slides
2011/2012
1 / 15
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Geometric Optics-College Physics B-Lecture 10 Slides-Physics and more Slides Physics in PDF only on Docsity!
PHY 2054C – College Physics B
Fall 2004
Electricity, Magnetism, Light Optics and Modern Physics Dr. Ingo Wiedenhöver Dr. A. Volya Today:
- Geometric Optics
- Focussing Mirrors
- Refraction and Total Internal Reflection
Last Lecture:
Wavelength and Frequency
If we look at the wave pattern at one time, we see the above pattern in space. The distance between two maxima is the wavelength λ. Now imagine the wave zooming past you with speed c: It takes period time T for one full cycle. The frequency f is number of cycles per second λ c = T ⇔ = c T ⇔ T = c f = 1 T = c
Question
What does the bottom figure represent?
- Wave is physically not possible
- Red light.
- Blue light. Green light: ???
Optics: How do we see things?
The different colors of light correspond to em waves of different wavelengths ?: White light contains a mixture of all wavelengths: When white light encounters matter, five things can happen: a) It is absorbed (by black objects) b) It is absorbed and re-emitted in a different direction (by white objects) (by white objects) c) It is absorbed and only some wavelengths are re-emitted (by colored objects) d) It is reflected (by smooth metal surfaces) e) It passes through matter (in transparent objects) or a combination of the above
Mirror- Images
The light rays emitted from the object are reflected in the mirror. To the observer, they appear to come from the image. object distance =image distance, d =d Light rays are emitted from an object in all directions. We only draw some rays, which reach the observer. We find out, where and how images are formed. “virtual image”
Focussing Light: Concave Mirrors
Parabolic Mirrors are used to focus parallel light (approximation: spherical mirrors) Parallel rays which enter on axis all are focussed towards the focal point. The focal length of a spherical mirror is f = r/2. Rays from objects which are very far away are almost parallel!
Mirror Equations
The focal length, object- and image distances are related by The lateral magnification is the ratio of the size of image over object;
f
d
O
d
I
m =
h
I
h
O
− d
I
d
O
Index of Refraction
When light enters a medium, its speed changes, it slows down! The index of refraction, e.g. the speed of light in water
n =
c
v
, n ≥ 1
Material n
Vacuum 1.
Air 1.
Water 1.
Glass 1.
Diamond 2.
v =
3 × 10
8
m /s
=2.25× 10
8
m /s
v = c n
E
Question 2
A fish swims below the surface of the water at P. An observer at O sees the fish at
- a greater depth than it really is.
- the same depth.
- a smaller depth than it really is.
Total Internal Reflection
When light passes from “denser” to “thinner” material, it follows snell's law: The maximum θ 1 , for which refraction possible (θ C
Beyond θ C , there is total internal reflection. Reflected ray 2 = 90 ° n 2 sin 2 = n 1 sin 1 sin 90 ° = 1 sin C = n 2 n 1