chapter 22 reflection and refraction of light 1. dual nature of light 2. geometric optics 3....
TRANSCRIPT
Chapter 22
Reflection and Refraction of Light1. Dual nature of light2. Geometric optics3. Reflection and Refraction4. Dispersion5. Huygen’s Principle6. Total Internal Reflection
A Brief History of Light 1000 AD
It was proposed that light consisted of tiny particles
Newton Used this particle model to explain
reflection and refraction Huygens
1678 Explained many properties of light by
proposing light was wave-like
A Brief History of Light, cont Young
1801 Strong support for wave theory by
showing interference Maxwell
1865 Electromagnetic waves travel at the
speed of light
A Brief History of Light, final Planck
EM radiation is quantized Implies particles
Explained light spectrum emitted by hot objects
Einstein Particle nature of light Explained the photoelectric effect
The Particle Nature of Light What is a photon? How do I calculate its energy? Can photon have a wave nature? What about experiments to test
such theories? Can a single experiment test dual
nature of light?
Ray Approximation & Geometric Optics
What is a wave front?
What is a Ray? What is the
purpose of a ray?
Specular and Diffuse Reflection
Law of Reflection What is it?
Example
1. Two mirrors make an angle of 120° with each other. A ray is incident on mirror M1 at an angle of 65° to the normal. Find the angle the ray makes with the normal to M2 after it is reflected from both mirrors
Refraction of Light What is
refraction? Snell’s Law
Two cases of Refraction
The Index of Refraction What is index of
refraction? How do I calculate it? What are its units? Some typical
examples What happens when
light passes from one medium to another?
An alternate formula
Some Indices of Refraction
Example
1. An underwater scuba diver sees the Sun at an apparent angle of 45.0° from the vertical. What is the actual direction of the Sun?
Example
1. Find the speed of light in flint glass.
Dispersion What is dispersion? Wavelength vs. n for
visible light. How does Snell’s law
play into this?
Refraction in a Prism What is angle of
deviation, δ?
Example1. The index of refraction for violet light in
silica flint glass is 1.66 and that for red light is 1.62. What is the angular dispersion of visible light passing through a prism of apex angle 60.0°, if the angle of incidence is 50.0°.
Prism Spectrometer
What is a spectrometer? How do we use it? What is a spectrum? What is it useful for?
Reflection, Refraction and the Rainbow
Why do we see the rainbow?
Kirchhoff’s Laws of Radiation (1)
1. A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths and thus produce a continuous spectrum.
Kirchhoff’s Laws of Radiation (2)2. A low-density gas excited to emit light will
do so at specific wavelengths and thus produce an emission spectrum.
Light excites electrons in atoms to higher energy states
Transition back to lower states emits light at specific frequencies
Kirchhoff’s Laws of Radiation (3)3. If light comprising a continuous spectrum
passes through a cool, low-density gas, the result will be an absorption spectrum.
Light excites electrons in atoms to higher energy states
Frequencies corresponding to the transition energies are absorbed from the continuous spectrum.
The Spectra of StarsInner, dense layers of a
star produce a continuous (blackbody) spectrum.
Cooler surface layers absorb light at specific frequencies.
=> Spectra of stars are absorption spectra.
Christian Huygens 1629 – 1695 Best known for
contributions to fields of optics and dynamics
Deduced the laws of reflection and refraction
Explained double refraction
Huygen’s Principle What is Huygen’s
principle? How do I apply it for
plane waves? How do I apply it to
spherical waves? What is the
difference between spherical and plane?
Why do I even need to know it?
Total Internal Reflection What is Total internal
reflection? What is critical
angle? How do I calculate it? When is total
internal reflection possible?
Example
1. A small underwater pool light is 1.0m below the surface. The light emerging from the water forms a circle on the water surface. What is the diameter of this circle?
Total Internal Reflection and Fiber Optics Applications
Surgical techniques Telecommunications Industry
What are the advantages?
Noise Light loss