Chapter 7Light and Geometric

Optics

7.1 Reflection

Heat Transfer by Radiation• Energy transmitted via RADIATION will be in the form of

ELECTROMANETIC WAVES and will travel at the SPEED OF LIGHT

Heat Transfer by RadiationThe various forms of RADIANT ENERGY (which originate

in the SUN)

The Electromagnetic Spectrum

All the different forms of electromagnetic radiation that

occur in nature =

Wavelength – Frequency – Energy long

Wavelength =low Frequency =low Energy

Wavelength – Frequency – Energy short Wavelength =

high Frequency =high Energy

Visible Light• light that our eyes can detect• visible light can be separated into its colors using prisms

Infrared Radiation• has the greatest heating effect• Provides most of the thermal energy requirements of the planet

Infrared Radiation

Ultraviolet Radiation• DAMAGING: responsible for sun tans and

sun burns

Ultraviolet Radiation•Black Lights are sources of UV Radiation

Linear Propagation Of Light•Light travel in straight lines (most of the time)

•Even thought the light has a wave – like properties it can be approximated as rays

rays = straight arrows

Ray Diagrams Ray of light is coming from the top of the candle and

moving towards the mirror For you to see the image of the candle in the mirror,

the light needs to be reflected back to your eye We complete the diagram by drawing another ray

pointed to the direction of the eye

The Law of ReflectionA ray approaching a mirror is called: INCIDENT RAY

A ray that is reflected by a mirror is called: REFLECTED RAY

The dashed line perpendicular to the mirror: THE NORMAL

The Law of ReflectionThe angle between the INCIDENT RAY and NORMAL:

THE ANGLE OF INCIDENCEThe angle between the REFLECTED RAY and

NORMAL: THE ANGLE OF REFLECTION

The Law of ReflectionINCOMING and REFLECTED angles are

EQUAL

The Image Formation in a Plane Mirror Flat mirror = a PLANE MIRROR

The Image Formation in a Plane Mirror• If an object is placed at a distance in front of a flat mirror

and light is bounced off the object and reflect from the mirror’s surface. • These rays appear to come from a location on the other side of the mirror. As a convention, an object’s image is said to be at this location behind the mirror because the light appears to come from that point.

Virtual Image

A VIRTUAL IMAGE• The image formed by rays that appear to come from the image point

behind the mirror—but never really do—is called a

A VIRTUAL IMAGE• The image formed by rays that appear to come from the image point

behind the mirror—but never really do—is called a

An exact reflection of the real object:

1. Same size as the original object

2. It is upright3. Same distance from

the mirror as the object is from the mirror (p = q)

p = object distanceq = image distance

4. Image is REVERSED

A VIRTUAL IMAGE• The image formed by rays that appear to come from the image point

behind the mirror—but never really do—is called a

An exact reflection of the real object:

1. Same size as the original object

2. It is upright3. Same distance from

the mirror as the object is from the mirror (p = q)

p = object distanceq = image distance

4. Image is REVERSED

DRAWING A VIRTUAL IMAGE

Same distance from the mirror

1 m

The dark outside allows you to see reflection from glass

behind

Less of your image is viewable

7.1 Review Questions (all)