Light is electromagnetic radiation that interacts with matter. It has wave-like properties such as frequency and wavelength and can behave as particles called photons. Light has various sources including emission from charges and luminous sources like the sun. It exhibits properties of reflection, refraction, interference and diffraction. Energy exists in various forms and transforms between forms, but the total amount of energy remains constant according to the law of conservation of energy. Future energy sources may include solar, geothermal, hydrogen and nuclear fusion to supplement current fossil fuel and nuclear fission sources.

1. Let There
Be Light

2. WHAT IS LIGHT?
Light is electromagnetic radiation– energy –
that interacts with matter.

3. STRUCTURE
• Regenerating co-
oscillation of electric
and magnetic fields
• Transverse waves
• Electromagnetic
spectrum

4. SOURCES OF LIGHT
• Emission - charges produce waves
• Absorption - waves accelerate charges
• Luminous
• Producing light
• The Sun versus the nonluminous Moon
• Incandescent
• Glowing with visible light from high temperatures
• Examples: flames, incandescent light bulbs

5. PROPERTIES OF LIGHT
Light ray model
• Particle-like view
• Photons travel in straight
lines
• Applications
• Mirrors
• Prisms
• Lenses
Wave model
• Traces motions of wave
fronts
• Best explains
• Interference
• Diffraction
• Polarization

6. LIGHT INTERACTS WITH
MATTER
• Interaction begins at surface and
depends on
• Smoothness of surface
• Nature of the material
• Angle of incidence
• Possible interactions
• Absorption and transmission
• Reflection
• Refraction

7. DIFFUSE REFLECTION
• Most common visibility
mechanism
• Each point reflects light in
all directions
• Bundles of light from
object are seen by the eye
• Colors result from
selective wavelength
reflection/absorption

8. IMAGE FORMATION
• Real image
• Can be viewed or displayed at its location
• Example - movie image on a screen
• Virtual image
• Appears to come from a location where it is not
directly visible
• Examples: plane mirror, convex mirror, concave mirror

9. REFRACTION
• Light crossing a
boundary surface and
changing direction
• Reason: change in
light propagation
speed

10. DISPERSION AND COLORS
• White light
• Mixture of colors in sunlight
• Separated with a prism
• Dispersion
• Different wavelengths
refract at different angles
• Violet refracted most (blue
sky)
• Red refracted least (red
sunsets)

11. OPTICS
• The use of lenses to form images
• Concave lenses
• Diverging lenses
• Vision correction/in association
with other lenses
• Convex lenses
• Converging lenses
• Most commonly used lens
• Magnifiers, cameras, eyeglasses,
telescopes, …

12. SPECIAL RELATIVITY
• Concerned with events as observed from different
points of view
• Based upon Einstein’s principles of
• Consistent law principle
• Constancy of speed principle

13. SPECIAL RELATIVITY
• Shows that measurements of
length, time, and mass are
different in different moving
reference frames
• The length of an object is
shorter when moving.
• Moving clocks run more slowly.
• Moving objects have increased
mass.

14. GENERAL THEORY OF
RELATIVITY
• Also called Einstein’s geometric theory of gravity
• Gravitational interaction is the result of the
interaction between mass and the geometry of
space
• 4th
dimensional “spacetime” structure

15. EVERYDAY USE OF
RELATIVITY
• Global Positioning System (GPS)
 locator in cell phones
 car navigation systems
• GPS is a worldwide network of 24 satellites, each
with an atomic clock that keeps accurate time to
within 3 nanoseconds (0.000000003 of a second)

16. WHAT IS ENERGY
Energy is
transformed
through working
or heating, and
the total amount
remains
constant.

17. FUNDAMENTAL LAW:
CONSERVATION OF ENERGY
Manifestations:
• Work, motion, position, radiation (light), heat,
chemical and nuclear energy, mass itself
Sources:
• Petroleum, coal, moving water, nuclear, solar
Uses:
• Transportation, generation of electricity, heating,
cooling, lighting

18. WORK
• Work is a product of
the applied force and
the parallel distance
through which the
force acts.
• W=Fd

19. WORK
A. Maximum work is if
the force (wind) is in
the same direction as
the plane’s change of
position.
B. If the force is not
parallel to
movement, work
done is reduced.

20. SIMPLE MACHINES
• Basic premise: work in
equals work out
• Examples
• Inclined plane
• Wedge
• Screw
• Lever
• Wheel and axle
• Pulley
Findin = Foutdout

21. POWER
• The rate at which work
is done or the rate at
which energy is
transformed.
• P = W/t

22. MOTION, POSITION AND
ENERGY
• Work and energy
related
• Energy = ability to do
work
• Work = process of
changing energy level
Next:
• Relationship between
work and energy
associated with
position
• Relationship between
work and energy of
motion

23. POTENTIAL ENERGY
• Energy associated with
position
• Gravitational potential
energy
• Also: elastic (springs) and
electric (charges)
potential energy
• Work can change PE
• Kinetic energy can change
into potential energy

24. KINETIC ENERGY
• Energy associated with
motion
• Results from work or
change in potential
energy
• Speed squared!
(Double speed, KE
increases by 4)

25. ENERGY FLOW
Energy can do work as
• Work against inertia
• Work against gravity
• Work against friction
• Work against shape
• Work against
combinations of above

26. ENERGY FORMS
Mechanical energy
• Kinetic plus potential
energy
Electrical energy
• Charges, currents, etc.
Chemical energy
• Energy involved in
chemical reactions
Radiant energy
• Electromagnetic energy
• Visible light = small part of
full spectrum
Nuclear energy
• Energy involving the
nucleus and nuclear
reactions

27. ENERGY CONVERSION
• Any form of energy can
be converted into
another form.
• Energy flows from one
form to another in
natural processes.
• Example - pendulum

28. CONSERVATION AND FLOW
OF ENERGY
Energy is never created or
destroyed. Energy can
be converted from one
form to another, but the
total energy remains
constant.

29. ENERGY SOURCES TODAY
• Primarily wood to coal
to petroleum with
increasing
industrialization
• 89% can be traced to
photosynthesis
• Uses
• ⅓ burned for heating
• ⅔ burned in engines
and generators

30. PETROLEUM
• Oil from oil-bearing rock
• Organic sediments transformed over time by
bacteria, pressure and temperature
• Natural gas formation similar, except at generally
higher temperatures
• Petroleum and natural gas often found together
• Supplies are limited: 25% from offshore wells,
over 50% imported

31. COAL
• Accumulated plant materials, processed over time
by pressure and temperature
• Progression: peat to lignite to sub-bituminous to
bituminous
• Impurities
• Minerals lead to ash
• Sulfur leads to sulfur dioxide gas (pollutant)
• Petroleum, natural gas and coal = fossil fuels

32. MOVING WATER
• Renewable with rainfall
• Gravitational potential energy of water converted
to electrical energy
• Hydroelectric plants generate ~3% of US’s total
energy consumption
• Growth potential limited by decreasing availability
of new sites

33. NUCLEAR
• Based on nuclear fission reactions of uranium and
plutonium
• Water heated in reactor and then used to produce
steam to turn generating turbines
• Safety of nuclear power generation is
controversial

34. ENERGY SOURCES
TOMORROW
Alternative source of energy: one that is different
from those commonly used today
Tomorrow: solar,
geothermal,
hydrogen gas,
fusion
Today: fossil fuels
(coal, petroleum,
natural gas), nuclear
and falling water

35. ENERGY CONSERVATION
• A way of reducing the need for additional energy
• Saves money for the consumer
• Can make demands easier to meet
• Energy efficiency improvements also reduce the need
for additional energy
• Much of the energy we consume is wasted –
individual and technological problem

36. SOLAR TECHNOLOGIES
• Solar cells
• Direct conversion of
light to electricity
• Power tower
• Mirrors focus sunlight
to heat water for
steam generation
• Passive application
• Designs to use solar
energy flow naturally
• Active application
• Solar collector used to
heat water, air or
some liquid
• Then used for heating
or electric generation

37. SOLAR TECHNOLOGIES,
CONT.
• Wind energy
• Turbines generate electricity
• Wind often inconsistent
• Biomass
• Plant material formed by
photosynthesis
• Burned directly or converted
to other fuels
• Agriculture and industrial
heating
• Direct use of sunlight to dry
grain, cure paint, etc.
• Ocean thermal energy
conversion
• Uses temperature difference
between surface and ocean
depth to generate electricity

38. GEOTHERMAL ENERGY
• Hot, dry rock
• 85% of total resource
• Associated with volcanic
activity
• Geopressurized resources
• Underground reservoirs of
hot water containing
natural gas
• 14% of available resources
• Dry steam
• Very rare: only three
sites in US
• Hot water
• Makes up most of the
recoverable geothermal
resources
• Can be circulated directly
into homes, businesses,
farms and so on

39. HYDROGEN
• Energy storage and transport system
• Must be generated for utilization
• One possible source: water, H2O
• Clean
• Combustion produces water
• Possible problems
• Best stored as liquid hydrogen (cold!)
• Extremely flammable