LIGHT &GEOMETRIC OPTICS NEW TOPIC: PHYSICS LIGHT &GEOMETRIC OPTICS

THREE CHAPTERS CHAPTER 11: The Production & Reflection of Light 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, 11 Sheet: Uses of Electromagnetic Waves

What do you know already? 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

????????????????????????????????????? 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 Light travels at a very high speeds Light travels in straight lines 1.

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... has electrical & magnetic parts does not require a medium travels at the speed of light

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

ELECTROMAGNETIC SPECTRUM http://www.bbc.co.uk/schools/gcsebitesize/science/edexc el/waves/theelectromagneticspectrumact.shtml

Wavelength Wavelength Amplitude Crest Trough

A wave is a disturbance that moves through space, transferring energy from one point to another. Wavelength (nanometers, nm) - how long each individual wave is as measured from the peak to peak or trough to trough of a wave Frequency (Hertz, Hz) - the number of waves that pass a point per second

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.

high energy radiation low energy radiation

KEY POINT: = Higher Frequency Higher Energy = Lower Frequency LONGER (LARGER) WAVELENGTH (Big Sumo Wrestler/Goalie) SHORTER (SMALLER) WAVELENGTH (Small Sumo Wrestler/Goalie) = Lower Frequency Lower Energy = Higher Frequency Higher Energy

The wavelengths of light that humans can perceive with their eyes. 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 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 protects us from most of it. The UV light that does reach Earth can be harmful to the skin, causing sunburns. Can damage genes in the body and break apart DNA to cause mutations. Main sources are the sun and other stars

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, 11 Sheet: Uses of Electromagnetic Waves