NEW TOPIC: PHYSICS

LIGHT &GEOMETRIC

OPTICS

THREE CHAPTERS

CHAPTER 11: The Production & Reflection of Light

CHAPTER 12:The Refraction of Light

CHAPTER 13: Lenses & Optical Devices

CHAPTER 11

11.1 - What is Light? 11.2 - How is Light Produced? 11.3 - The Laser 11.4 - The Ray Model of Light 11.6 - The Laws of Reflection 11.7 - Images in a Plane Mirror 11.8 - Images in a Curved Mirror

TODAY:

11.1: WHAT IS LIGHT?READ PAGES: 461 - 469

Homework: Nelson Science Perspective 10:

Page 469 # 1, 4, 6, 8, 9, 11Sheet: Uses of Electromagnetic

Waves

TODAY:

What do you know already?Team up with a partner, discuss and answer the questions on page 457 on a blank sheet of looseleaf paper.

SECTION 11.1

Introduction to Light

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What is Light??

Light is a form of energy that travels in straight lines at a speed of 3 x 108 m/s through the vacuum of space and into our atmosphere. Light is a type of electromagnetic radiation, which is made up of wave patterns consisting of both electric and magnetic fields that move at right angles to each other.  

Properties of Light

1. Light travels at a very high speeds

Light travels in straight lines

Light...

travels through a vacuum

does NOT require a medium for transmission.

Is energy transferred through radiation.

What is a Medium?

A MEDIUM is any physical substance that acts as a carrier for the transmission of energy.

Conduction & Convection

Heat energy can be transferred by either conduction or convection.

Both conduction and convection require a MEDIUM for transmission. Conduction – solids Convection – liquids & gases

Light is energy transformed through radiation

Radiation is a method of energy transfer that does NOT require a medium.

Light is an Electromagnetic Wave

An electromagnetic wave is a wave that...

1. has electrical & magnetic

parts

2. does not require a medium

3. travels at the speed of light

The Electromagnetic Spectrum

Scientists have identified many different kinds of electromagnetic waves. A whole spectrum of them!

http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/waves/theelectromagneticspectrumact.shtml

ELECTROMAGNETIC SPECTRUM

Wavelength

Wavelength

Amplitude

Crest

Trough

A wave is a disturbance that moves through space, transferring energy from one point to another.

Frequency (Hertz, Hz) - the number of waves that pass a point per second

Wavelength (nanometers, nm) - how long each individual wave is as measured from the peak to peak or trough to trough of a wave

Wavelength and frequency are inversely

related to one another.

When the wavelength increases (becomes longer), the frequency decreases, resulting in low energy radiation.

When the wavelength decreases (becomes shorter), the frequency increases, resulting in high energy radiation.

low energy radiation

high energy radiation

KEY POINT:

= Lower Frequency

= Lower Energy

= Higher Frequency

= Higher Energy

LONGER (LARGER) WAVELENGTH

(Big Sumo Wrestler/Goalie)

SHORTER (SMALLER) WAVELENGTH

(Small Sumo Wrestler/Goalie)

Visible Light

The wavelengths of light

that humans

can perceive with their

eyes.

“ROYGBIV”

Of the different types of electromagnetic waves, visible light is the only one that humans can see.  This visible spectrum known as white light is composed of seven different colors.

Newton was the first scientist to study color. He passed sunlight through a prism and found that it could be separated into beams of light of different colors. He showed that visible light actually consists of red, orange, yellow, green, blue, and violet light. Each of these colors corresponds to a particular frequency and wavelength of light.

White Light & Prisms

In vacuum, all colors travel at the same speed (= speed of light).

The triangular prism slows down the speed of light, but by different amounts...

Red Light = Least Energetic = Slowed Least = Travel Fastest.

Violet Light = Most Energetic = Slowed Most = Travel Slowest.

Prism can separate white light into different colors.

Infrared (IR) Light – HEAT!

INFRARED (IR) Photography

Ultraviolet

Only some of the Sun’s ultraviolet light reaches the Earth – the ozone layer

protectsus from most of it. The UV

lightthat does reach Earth can be harmful to the skin, causing sunburns.

Ultraviolet (UV) Light

X-Rays

Used in doctor’s offices to see bones, but are

also produced in space by violent processes.

However, these wavelengths are unable to get

through to our lower atmosphere.

Aside: Bees are Incredible!

Many species, including bees, can see a broader spectrum of light than we can!

Bees have UV-sensitive photoreceptors in their eyes that allow them to see UV light (humans cannot see UV light)!

There are certain pigments in flower petals that absorb UV light and create patterns visible to bees (but invisible to humans).

These patterns are referred to as“honey guides” or “nectar guides.”

They serve to direct the pollinators toward the center of flowers where the pollen is located.

Did You Know…

Goldfish can see infrared radiation that is invisible to us. Bees, birds, and lizards

have eyes that pick up ultraviolet light.

Sources of Light

Light sources can be natural (coming from the

Sun) or artificial (coming from a light bulb or

candle).

TODAY:

11.1: WHAT IS LIGHT?READ PAGES: 461 - 469

Homework: Nelson Science Perspective 10:

Page 469 # 1, 4, 6, 8, 9, 11Sheet: Uses of Electromagnetic

Waves