PHYS 1C Lecture Notes - Lecture 13: Double-Slit Experiment, Specular Reflection, Refraction
Light has a 'dual' nature in that it can act both as a particle and a
wave. Particles and waves exhibit very different properties, so
this is weird! Particles are localized objects, waves are a non-
localized traveling pattern/disturbance in medium. Waves
create interference, particles do not.
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In some experiments, light acts like a wave (double slit
experiment), but in other experiments it acts like a particle
(photoelectric effect - later this term). In quantum mechanics
the wave-particle duality isn't so strange, but in classical
mechanics it is
-
From now on we will have to treat light as having both wave and
particle properties
-
As light moves through a medium (such as air) it will move in a
straight line path
-
We draw imaginary lines (known as light rays) to represent this
path
-
We can also represent this motion with wave fronts
-
A wave front is a surface where the wave has the same phase
and amplitude
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The Nature of Light
Light rays travel in straight lines in a given medium
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Light rays can cross. They do not interact with each other. Two
rays can cross without either being affected in any way
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A light ray travels forever unless it interacts with matter
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It can interact with matter by either: reflection, refraction,
scattering or absorption
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An object is a source of light rays
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Rays originate from every point on the object, and each point
sends rays in all directions
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If the object is far away, the rays will appear parallel to the
observer
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We make no distinction between self-luminous objects and
reflective objects
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The eyes sees by focusing a diverging bundle of rays
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Ray Model of Light
The incident light ray will move in a straight line path as long as
the medium does not change
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But, when it encounters a boundary with a second medium, (at
least) part of this incident ray is reflected back into the first
medium
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If the boundary is a smooth surface, the reflection is known as
specular reflection
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This means all the reflected rays will be parallel to one another
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The Nature of Light
We define a normal (perpendicular line to the surface) at the
point where the incident ray hits the surface
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The incident angle is the angle that the incident ray makes with
respect to the normal
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Law of Reflection
(13) Lecture 25A Reflection and Refraction
Friday, May 4, 2018
12:49 PM
week 5 Page 1
Document Summary
Light has a "dual" nature in that it can act both as a particle and a wave. Particles and waves exhibit very different properties, so this is weird! Particles are localized objects, waves are a non- localized traveling pattern/disturbance in medium. In some experiments, light acts like a wave (double slit experiment), but in other experiments it acts like a particle (photoelectric effect - later this term). In quantum mechanics the wave-particle duality isn"t so strange, but in classical mechanics it is. From now on we will have to treat light as having both wave and particle properties. As light moves through a medium (such as air) it will move in a straight line path. We draw imaginary lines (known as light rays) to represent this path. We can also represent this motion with wave fronts. A wave front is a surface where the wave has the same phase and amplitude.
