Science 8 - Unit 3 What is Light & the Types of Light

Thermal Energy?

-AKA heat -Absorbs light from dark & dull objects -turns objects warmer EX: The sun hits black hair and the hair absorbs heat & becomes very hot.

Why do some organisms emit sources of light?

-Attraction of prey -Attraction of mates -Scaring off predators -Chemical reactions

Fluorescence?

-Emission of light produced by ULTRAVIOLET light particles -coming out as visible light Ex: CFL lightbulbs, fluorescent light etc.

Bioluminescence?

-Emission of light produced by chemical reactions inside the bodies of living creatures. Ex: glow worms, anglerfish, jellyfish etc.

Chemiluminescence?

-Emission of light resulting from chemical action -Doesn't involve heat Ex: LED light, glow stick etc.

Incandescence?

-Emission of light through friction, using heat & a filament Ex: fire, matches etc.

Phosphorescence?

-Emission of visible light following the removal of a source of radiation Ex: glowing watch face, glow in the dark toys.

What is light pollution, how does it affect us?

-Extra light being added into the environment Ex: Street lights illuminating the sky too much. -it can cause people to feel uncomfortable, their eyes can't take the light -difficult to live in for animals and their needs -it blocks out the view of the sky

Electrical Energy?

-Light forms to make electricity EX: Solar cells change light into electricity. (For solar calculators, solar panels etc.) Chargers in an outlet to power electronics.

Luminous?

-Something perceived by the eye -Something very bright or colourful -Something shining

Chemical Energy?

-Stored in chemical compounds -Released by chemical reactions -often produces heat EX: Trees absorbs sunlight to form chemical energy for photosynthesis.

Give a summary of Chemiluminescence.

-no big heat radiation -chemical action -chemical energy -ex: glowsticks

Give a summary of Bioluminescence.

-organisms with light sources -chemical reactions -ex: jellyfish

What are some ways people are resolving the problem of light pollution?

-street lights only pointing downwards -yellow sodium vapour lights -solar panels

Give a summary of Phosphorescence.

-type of fluorescent light -"glow in the dark" -no heat radiation -ex: glow in the dark toys

Give a summary of Fluorescence.

-ultraviolet light is used -high energy use -invisible until electrons & UV light is together -ex: CFL light

Give a summary of Incandescence.

-uses friction -produces heat -uses filaments -ex: lightbulb

Show the energy transformation of bioluminescence. (use 3 steps.)

1. Chemical energy 2. Chemical reaction 3. Visible light energy

Show the energy transformation of chemiluminescence. (use 3 steps.)

1. Chemical energy 2. Chemical reaction 3. Visible light energy

Show the energy pathway for a fluorescent source of light. (Use 5 steps.)

1. Electrical energy 2. Energy absorbed by mercury particles 3. Ultraviolet energy 4. Energy absorbed by phosphor particles 5. Visible light energy

Show the energy pathway for Incandescence. (Use 3 steps.)

1. Electrical energy 2. Thermal energy 3. Visible light energy

Show the energy transformation of phosphorescent light sources. (use 3 steps.)

1. Light energy 2. Energy absorbed by particles 3. Visible light energy

What is 1 difference between phosphorescent light sources and fluorescent light sources?

1. Phosphorescence doesn't immediately re-emit the radiation it absorbs. It holds onto energy longer and re-emits it later. But fluorescence re-emits immediately. ex: a toy ball glows AFTER you hold it near a bright light for a while.

What are 2 things light can do when it hits a surface?

1. Reflect off the surface 2. Absorb into the surface as HEAT

List 3 types of energy light can be transformed into.

1. Thermal 2. Chemical 3. Electrical

Show the energy transformation for fluorescent light sources. (Use 3 steps.)

1. Ultraviolet light energy 2. Energy absorbed by particles 3. Visible light energy

About ____% of the energy given off by incandescent light bulbs are released as heat.

95%

Why are fluorescent lights so expensive?

Because the mercury contained in them are TOXIC & POISONOUS.

Light

A form of energy that is viewable.

What is a manufactured light source?

A source of light that's created by humans. (ex: light bulb, matches)

What is a natural light source?

A source of light that's created by nature. (ex: fire, the sun)

What are 2 advantages & disadvantages of using fluorescent light sources (in comparison to using incandescent light sources)?

Advantages: 1. energy efficient, uses less for larger areas 2. not heated, you can touch lit tubes Disadvantages: 1. expensive 2. difficult to dispose (the phosphor & mercury coatings are TOXIC)

What energy do fluorescent light sources use?

Electrical

True or False? Incandescent light sources DON'T use filaments.

FALSE Incandescent light sources use filaments.

What kind of vapour particles are inside fluorescent tubes that emit ultraviolet light?

MERCURY VAPOUR PARTICLES. They absorb ELECTRICAL energy to emit ULTRAVIOLET LIGHT.

When Ultraviolet light is emitted, is it visible?

NO, Ultraviolet light is invisible.

Light that leaves the sun is formed through a process called?

Nuclear Fusion

What kind of white powder is used in a fluorescent tube to create VISIBLE LIGHT?

PHOSPHOR powder, it hits the ULTRAVIOLET LIGHT in the fluorescent tube which creates VISIBLE LIGHT.

What is it called when light spreads out in ALL directions?

Radiation (Radiant Energy)

True or False? Fluorescent light sources are expensive.

TRUE

True or False? Phosphorescence is related to Fluorescence.

TRUE The difference is that, phosphorescent particles that absorb energy DON'T release immediately.

True or False? Chemical reactions provide energy for chemiluminescent and bioluminescent sources.

TRUE They both use chemical energy.

Intensity?

The harshness and brightness of a light, how much energy a surface will get.