What is light?

Light

Make a list of things that give us light.How many can you think of?

Light

• Light is form of _______ that you can _____.• Light is on kind of _____________.• Light comes from ______ different _______.• Some items _______ light while others ______

light.

energy seeradiant energymany sources

producereflect

Light

• Is it a producer or a reflector?– Candle producer

reflector– Mirror producer

reflector– Sun producer reflector– Flashlight producer reflector– Jupiter producer

reflector

Light

• Name four other objects that produce light.

firestarslanternLight bulblamplasercandles

lightningThe sunFirefliesFlashlights

Light

• Name four other objects that reflect light.

The moonMetalGlassWaterMirrorsSnowFlashlights

How Does Light Travel?

• Light ______ in a __________.• Can you think of some real-life examples of

light traveling in a straight line?

travels straight line

FlashlightLaserLamp

Reflection

• Light can be ________ or ________ by a surface.

• When light is ________, it __________ that surface.– Example: ________

• When light is _________, it is _______ by that surface.– Example: __________

• Light is _________ off a surface in a special way.

reflected absorbed

reflected Bounces off

mirrorabsorbed trapped

Your bodyreflected

Light Reflection

• The angle at which light __________ a surface is the ________________.

• The angle of incidence is = to the angle of reflection.

• Example: When _____ strikes a ______ at a ____ angle, it is reflected at a ____ angle.

reflects offangle of reflection

light mirror45 45

Reflected, Absorbed, or Transmitted?

• Light that _____________ matter is __________ by the material.

• If light is not __________, some of it is ________.

• If light is not __________ or ________, it is ________.

passes throughtransmitted

transmittedreflected

transmitted reflectedabsorbed

Reflected, Absorbed, or Transmitted?

• There are three types of materials:1. Transparent:

2. Translucent:

3. Opaque:

light is transmitted (passes through)

some light is transmitted, some is reflected and scattered

light is absorbed (not transmitted or reflected)

Transparent, Translucent, or Opaque?

Transparent Translucent Opaque

Refraction

• When an object is placed in a glass of _____ it appears to be ________________________. This is because of light ________.

• Light changes ________ when it enters a new ________.• A medium is any _________ through which a _____ is

__________.• Example: ____ is traveling from the overhead light bulbs

through ___. When the _______ enters the cup of _____, it enters a new ________. This causes the _____ to change _________.

waterbroken or shifted to the side

refractiondirection

mediumsubstance wave

transmittedLight

air lightwater medium

light direction

Refraction

• Light in ___ travels ____.• Light in _____ travels ___________.• When light ___________, it changes ________.• When light changes ________ or _____, it is

called _________.• _________is caused by the change of the

____________ as it travels through different ________.

air fastwater more slowly

slows downdirection

direction bendsrefraction

Refractionspeed of lightmediums

Speed of Light

• The speed of light is _____________________• That is the same as _____________________ ______________.• This is how fast light travels in ___. When it

enters a new ________ (like water), it slows down. The result is _________.

186,000 miles per second 7.5 times around the

Earth in 1 secondair

mediumrefraction

Speed of Light

Light from the sun takes about 8 minutes to go 93 million miles to Earth. If you could drive to the sun at 60 mph it would take you 177 years!

Light moves perfectly straight until something bends it.

Color of Light

• Light _______ in ______.travels waves

Color of Light

• __________ is the measure of the number of ______ that pass by a given point in one second.

• Remember, ______ is one kind of _______energy.• Radiant energy includes ______ of all different

___________ and ___________.• When all the types of _____________ are

arranged in ______, we have the _______________________.

Frequencywaves

light radiantwaves

wavelengths frequenciesRadiant energy

orderElectromagnetic Spectrum

Color of Light

Color of Light

Infrared: We often think of this as being the same thing as ‘heat’, because it makes our skin feel warm. In space, IR light maps the dust between stars.

Color of Light

Visible: Yes, this is the part that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars…also by fast-moving particles hitting other particles.

Color of Light

Ultraviolet: We know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn! Stars and other “hot” objects in space emit UV radiation.

Color of Light

X-rays: Your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the Universe also emit X-rays.

Color of Light

Gamma-rays: Radioactive materials (some natural and others made by man in things like nuclear power plants) can emit gamma-rays. Big particle accelerators that scientists use to help them understand what matter is made of can sometimes generate gamma-rays. But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways.

Visible light

• We can only see one portion of the electromagnetic spectrum. That portion is called __________.

• What color is the light from most light bulbs?• Although we see _____ light, it is actually made up

of many ______.• The colors of the spectrum are: ____________ ______________________An easy way to remember these colors in order is __________

visible lightwhite

whitecolors

red, orange, yellow, green, blue, violet

ROY G. BiV

Activity: Blending Light

• The primary colors of light are red, green, and blue.

• What happens if we mix them together?

Colors

• If light is made of all the colors of the spectrum, how do we see certain colors?

• Why do we see white, black, or red?

Colors

Why we see white:• All the colors of the spectrum strike the surface.• All the colors of the spectrum are reflected to our

eyes.

Colors

Why we see black:• All the colors of the spectrum strike the surface.• All the colors of the spectrum are absorbed.

(None are reflected)

Colors

Why we see red:• All the colors of the spectrum strike the surface.• Red is reflected to our eyes.• The rest of the colors are absorbed.

Colors

Now try two on your own…• Why we see yellow:

• Why we see green:

• All the colors of the spectrum strike the surface.• Yellow is reflected to our eyes.• The rest of the colors are absorbed.

• All the colors of the spectrum strike the surface.• Green is reflected to our eyes.• The rest of the colors are absorbed.

Summary

• Light can be ________ (__________)• Light can be ________ (______)• Light can be ________ (____)• Light can be _________ (_____________)

reflected bounced off

absorbed trappedrefracted bentseparated creates rainbow