# Light Online

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Published on January 31, 2008

Author: ewingj

Source: slideshare.net

Light

Facts Light is energy – electromagnetic energy (energy that is electric and magnetic) Travels in a straight path unless…it goes through a new material (medium) then it may bend or slow down Travels in waves Travels VERY fast! The speed of light: 186,000 mi/sec

Light is energy – electromagnetic energy (energy that is electric and magnetic)

Travels in a straight path unless…it goes through a new material (medium) then it may bend or slow down

Travels in waves

Travels VERY fast!

The speed of light: 186,000 mi/sec

How fast is 186,000 miles/second?

Wavelengths We measure the length of a light wave by measuring between two crests (high points) or troughs (low points). If the waves are close together, it has a short wave length. Far apart = long wave length

We measure the length of a light wave by measuring between two crests (high points) or troughs (low points).

If the waves are close together, it has a short wave length.

Far apart = long wave length

When light hits a surface, it bounces or REFLECTS off of the surface. If light hits a smooth surface, it will bounce at a predictable angle. If light hits a rough surface, it bounces off at all kinds of angles.

When light hits a surface, it bounces or REFLECTS off of the surface.

If light hits a smooth surface, it will bounce at a predictable angle.

If light hits a rough surface, it bounces off at all kinds of angles.

Look at how the surface affects these water reflections.

Con cave mirrors curve inward-like a “ cave ” Close up – image is enlarged, right-side up Further away – image is enlarged, but upside-down The further away you move, the smaller the image gets

curve inward-like a “ cave ”

Close up – image is enlarged, right-side up

Further away – image is enlarged, but upside-down

The further away you move, the smaller the image gets

Convex Mirrors curve outward The image is always smaller and right-side up. Used for side view mirrors on cars, to prevent shoplifting, and in our stairwells here at school.

curve outward

The image is always smaller and right-side up.

Used for side view mirrors on cars, to prevent shoplifting, and in our stairwells here at school.

Which is convex? Which is concave?

How light passes through objects Opaque completely blocks light from coming through Translucent Lets only part of the light through View is blurry Transparent Allows light to pass through with almost no disturbance Can be clear or colored Clear view

Opaque

completely blocks light from coming through

Translucent

Lets only part of the light through

View is blurry

Transparent

Allows light to pass through with almost no disturbance

Can be clear or colored

Clear view

Refraction When light rays bend as they are passing from one substance to another Happens when light rays pass through at an angle

When light rays bend as they are passing from one substance to another

Happens when light rays pass through at an angle

Lenses – curved transparent materials that refract (bend) light to make images Convex lenses Curve out Light rays bend together after passing through “ e ” in conv e x = tog e ther

Lenses – curved transparent materials that refract (bend) light to make images

Convex lenses

Curve out

Light rays bend together after passing through

“ e ” in conv e x = tog e ther

Convex lens – the rays angle together If the lens is close to your eye, the image you see will be right-side up and enlarged. If the lens is further away, the image will be upside down.

If the lens is close to your eye, the image you see will be right-side up and enlarged.

If the lens is further away, the image will be upside down.

Concave Lenses Curves inward (like a cave) Light rays pass through and move apart “ a ” in conc a ve = apart

Curves inward (like a cave)

Light rays pass through and move apart

“ a ” in conc a ve = apart

Conc a ve Lens The image you see is always smaller and right-side up.

The image you see is always smaller and right-side up.

What would happen if you put both of them together? Hmm…..

Hmm…..

Visible Light Waves White light is actually all the colors of light combined Each color of light has a different wave length Red has the longest; violet the shortest.

White light is actually all the colors of light combined

Each color of light has a different wave length

Red has the longest; violet the shortest.

When the light ray passes through a prism, the rays bend at different angles because their wave lengths are different

Since red’s wavelengths are longer, they bend the least when passing through the prism Violet’s are shortest, so they bend the most.

Since red’s wavelengths are longer, they bend the least when passing through the prism

Violet’s are shortest, so they bend the most.

Visible Light Spectrum A rainbow acts as a prism and a mirror. The sun shines through the drops of water (prism) and the backside of the raindrop is like a mirror, reflecting the bent colors back to us. BrainPop Rainbow

A rainbow acts as a prism and a mirror. The sun shines through the drops of water (prism) and the backside of the raindrop is like a mirror, reflecting the bent colors back to us.

BrainPop Rainbow

ROY G BIV Helps us remember the colors of the visible light spectrum. R = red O = orange Y = yellow G = green B = blue I = indigo V = violet Review with BrainPop!!!

Helps us remember the colors of the visible light spectrum.

R = red

O = orange

Y = yellow

G = green

B = blue

I = indigo

V = violet

Review with BrainPop!!!

How does color work? When light hits an object, it either reflects (bounces off) or is absorbed. An object’s color depends on which light waves are absorbed or reflected. If an object is yellow, it’s because all the colors except yellow are absorbed by the object. The yellow light is reflected back and what we see yellow!!

When light hits an object, it either reflects (bounces off) or is absorbed.

An object’s color depends on which light waves are absorbed or reflected.

If an object is yellow, it’s because all the colors except yellow are absorbed by the object. The yellow light is reflected back and what we see yellow!!

If none of the light colors are absorbed, then all of them reflect, and the object looks white.

If none of the light colors are absorbed, then all of them reflect, and the object looks white.

If all are absorbed, no light is reflected, and the object looks black.

If all are absorbed, no light is reflected, and the object looks black.

Electromagnetic Spectrum Remember that visible light is electromagnetic energy that travels in waves Our eyes are only sensitive to the wavelengths of light from violet to red. Our eyes don’t pick up wavelengths shorter or longer than these

Remember that visible light is electromagnetic energy that travels in waves

Our eyes are only sensitive to the wavelengths of light from violet to red.

Our eyes don’t pick up wavelengths shorter or longer than these

Electromagnetic Spectrum

BrainPop - Electromagnetic Spectrum

BrainPop - Electromagnetic Spectrum

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