Science8 Unit C Lightand Optics Section3 Lesson6 Visible Light

Light is part of the electromagnetic

spectrum and travels in waves

Lesson #6, Section 3.3-3.4. Pages 221-229

Learner Outcomes I can evaluate, compare, and contrast

different artificial and natural light sources

I can describe how primary colours can be added to produce different colours and white light

ROY-G-BIV

Radiation is the wave like transfer of light from its source in all directions.

Light is often called radiant energy.

Light from the sun is formed by nuclear fusion.

Light is a form of energy When light reaches a surface, it can be absorbed and transformed into other types of energy.

… into electrical energy … into thermal energy … into chemical energy

The amount of energy a surface receives depends on

the intensity of the light.

The more intense the light, the more light can be

absorbed.

NATURAL LIGHT SOURCE ARTIFICIAL LIGHT SOURCE

Sun

Nuclear Fusion Thermal Energy Visible Light Energy

Incandescent (heat causing a filament of metal to glow - visible

light)

Electrical energy Thermal energy

Visible light energy

NATURAL LIGHT SOURCE ARTIFICIAL LIGHT SOURCE

Candles or Oil Lamps

Chemical energy Thermal Energy

Visible light energy

Florescent (ultraviolet light is absorbed by fabric

particles, which in turn emit some of the energy as

light - glowing)

Ultraviolet light Energy absorbed Visible light energy/particles energy

NATURAL LIGHT SOURCE ARTIFICIAL LIGHT SOURCE

Wood (fire)

Chemical energy Thermal Energy

Visible light energy

Phosphorescent (light energy is stored and

released later as visible light) paint

Chemical energy Visible light energy

NATURAL LIGHT SOURCE ARTIFICIAL LIGHT SOURCES

Bioluminescence (light produced by living organisms)

Chemical energy Visible light energy

Chemiluminescent (light energy released by

chemical reactions) glow sticks

Chemiluminescence

Movies (Shockwave/Flash)

Chemical energy Visible light energy

Incandescent light bulbs produce far more heat than light, or more infrared radiation than visible light energy. 95% heat vs. 5% light

Fluorescent bulbs are more efficient. 80% heat vs. 20% light

Read page 224 and complete this activity in groups of 3-5 people

Make sure you observe safety protocols

... evaluate, compare, and contrast different artificial and natural light sources?

#1. Explain how an incandescent light bulb works. ____________________________________________________________________________________

#2. Your watch dial may have glow in the dark numbers. Is this phosphorescence or fluorescence? Explain your answer. ________________________________________________________________________________________________________________________________________________________________________

#3. Why would a business choose fluorescent instead of incandescent lights? ____________________________________________________________________________________

#4. What is bioluminescence? Provide at least two examples. ______________________________________________________________________________________________________________________________

The various colors of the visible spectrum have slightly different wavelengths and refract by a slightly different amount.

The Primary colors of the visible spectrum are red, green and blue.

The Primary colors of the visible spectrum are red, green and blue.

Secondary colors are cyan, magenta and yellow.

The mixing of three colors of light to produce many different colors of light is called the theory of color addition.

Television puts the theory of color addition into practice.

By changing the brightness of the dots that make up the screen many different colors can be produced.

The television works by fooling the eye into seeing colors that are not really there.

The colour an object appears depends on the colours of light it reflects.

For example, a red book only reflects red light:

White

light

Only red light is reflected

A white hat would reflect all seven colours:

A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):

Purple light

White

light

If we look at a coloured object in coloured light we see something

different

White

light

Shorts look blue

Shirt looks red

Filters can be used to “block” out different colours of light:

Red Filter

Magenta Filter

... describe how primary colours can be added to produce different colours and white light?

#1. What are the primary colours of light? How is white light produced? ________________________________________________________________________________________________________________________

#2. Explain how a prism can determine what white light is composed of? ________________________________________________________________________________

#3. You are a lighting technician in a theatre. The director asks for magenta light on stage, but you only have red, blue, and green lights. What could you do to produce magenta light? ________________________________________________________________________________________________________________________________________________________________________________________________________