Unit 7 - Light and the Electromagnetic Spectrum

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Order the colors of visible light from LEAST to Most energy.
[blue, violet, green, yellow, orange, red]

red, orange, yellow, green, blue, violet.

Why is ultraviolet light more dangerous than visible light?

That's because it contains ionizing radiation, which can damage DNA.

What is true about the speed of all the light waves.

They are all the same.

What is the relationship between frequency and wavelength?

As frequency increases, the wavelength decreases.

What is the relationship between frequency and energy?

As energy increases, frequency also increases.

What is the relationship between wavelength and energy?

As wavelength decreases, the energy increases.

Retina

The back of the eye that contains photo receptors.

Rod cells

• Respond to light intensity (brightness).
• Respond to very dim light.
• Do not see color.
• There are a lot more of them than cone cells.

Cone cells

• Respond to the color of light.
• There are 3 types: blue, red, and green.

Physical color

Property of the object.

• Ex: pure yellow

True or False: We see the color red of an apple because the red light is absorbed.

False

Ionizing radiation examples

• Ultraviolet
• X-ray
• Gamma Ray

Non-ionizing radiation examples

• Radio
• Microwave
• Infrared

Which radiation is bad, because it breaks DNA.

Ionizing

Which type of cell allows us to see in dim light?

Rod

True or False: The speed of light changes with the frequency of the light.

False

True or False: There is only one kind of color blindness.

False

Which type of cell allows us to see color?

Cone

Which part of the eye contains the rod and cone cells?

Retina

Electromagnetic radiation is…

pure energy.

Ionizing radiation is damaging. The longer the exposure and/or the higher the energy…

the more damaging.

Red + Green

Yellow

Green + Blue

Cyan

Blue + Red

Magenta

Red + Green + Blue

White

What colors make up white light.

All colors of the rainbow.

How do color filters affect white light?

Color filters only allow one wavelength (the wavelength of the color filter) to go through. All the other colors are absorbed and aren't seen.

In general, what do color filters do?

They absorb all but one color and change the color that appears from the light.

The more the cone cell is triggered….

the more of that color you see.

What color does cyan subract?

Red

What color does magenta subtract?

Green

What color does yellow subract?

Blue

Pigments for printing or crayons

Subtractive

Human cone cells or light

Additive

Which EM waves carry information?

• Radio
• Microwaves
• Infared

The more energy a light wave carries…

the higher the amplitude and the brighter the light.

Information can be carried by a wave by changing what two things?

Amplitude or frequency

How fast does light travel?

300,000,000 m/s

What letter is the speed of light represented by?

c

What do electrons of atoms absorb?

Energy

What happens when the electron falls back down after getting excited and jumping to a higher energy level?

Light is released

Opaque

Light does not pass through.

• The light is all absorbed.

Translucent

Some light passes through, but you cannot see an image.

Transparent

Practically all light passes through, and you can see an image.

Ray, beam, line

Terms that mean the light path or the drawing of the light path.

Law of Reflection

States that i = r

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

Normal line

The line that is perpendicular to the mirror and starts where the laser hits the mirror.

Mirror

Something that reflects light.

Point of intersection

Where the laser's ray, mirror line, and the normal line meet.

Reflection

Light bounces off an object.

• How we see things.
• Can be explained in terms of waves and particles.

Refraction

The bending of a light wave when it passes from one medium to another.

• Can be explained in terms of waves, but sort of for particles.

Interference

The constructive and destructive interference caused when waves interact.

• Can be explained in terms of waves, but not particles.

Diffraction

The bending of a wave as it passes through a narrow gap.

• Can be explained in terms of waves, but not particles.

Polarization

Using a series of very thin slits to make all the light go in the same direction.

• Can be explained in terms of waves, but not particles.

Photoelectric Effect

When a particular frequency of light hits a type of metal and an electron is released.

• Can be explained in terms of particles, but not waves.

Photon

Particles of light that travel as wave packets.

• Each photon has its own color based on its frequency.

Optics

• The study of light and how we manipulate it.
• Also a device that manipulates light like mirrors, lenses, and prisms.

Prism

A solid piece of glass with flat polished surfaces that can both bend and reflect light.

• A triangle is the most common shape.

Lens

A device that bends light in a predictable way.

• They work by refracting light.

What type of lens is the one that's oval-like and curved outwards?

Double convex

What type of lens is the one that's flat on the top and curved inwards?

Double concave

What does a double convex lens do to an image?

It magnifies it.

What does a double concave lens do to an image?

It makes distant things clear.

Where is the focal point for a converging double convex lens?

Between the lens and the mirror.

Where is the focal point for a diverging double concave lens?

Between the light source and the lens.

A person on the show "Survivor" sees a fish in the water and wants to throw a spear to get the fish. What will happen if they aim directly at the fish? Why?

The person will not hit the fish because the fish is refracted in the water, making it appear in a different place than where it actually is.

A person from the future sees a fish in the water and wants to zap it with a laser. What will happen if they aim the laser at the fish? Why?

The laser will hit the fish because the laser beam will also refract the exact same way that the light did with the fish.

While opening your eyes underwater, your vision is very poor, but if you wear swimming goggles, it is fine. Using your knowledge of refraction, explain why.

That's because water bends light in a way that makes it hit behind our retina instead. Goggles allow the light traveling through the water to once again travel through the air surrounding the eyes and hit our retina.

Electromagnetic energy invisible to the human eye is:

Ultraviolet light

Light may be produced by heating a substance until it glows. This process is called:

Incandescence

The three additive primary colors of light are:

Red, green, and blue.

The three colors of pigments for the subtractive color process are:

Magenta, cyan, and yellow.

The main difference between cone cells and rod cells in the human eye is that:

Rod cells respond to light intensity and cone cells respond to color.

We see a tree because of light…

reflected by the tree.

If white light falls upon a piece of blue cloth, the cloth absorbs…

all colors except blue and reflects only blue light to our eyes.

Filters are transparent materials that may absorb some colors and transmit others as light passes through them. If white light shines through a red filter, the filter absorbs…

all the colors except red.

A converging lens changes the direction of light through the process of:

Refraction

The place where rays of light cross after they have been bent by a converging lens is known as the:

Focal point

The bending of light rays that occurs as light crosses a boundary from one substance to another is called:

Refraction

Prisms are triangular blocks of glass with flat, polished surfaces. How do prisms affect light? (2 ways)

Reflection and refraction

Which statement describes a diverging lens?

Light is bent away from the focal point.

The index of refraction best describes:

the ability of a material to bend light rays.

The lighting crew of a theater has three spotlights aimed at the same spot on center stage, one blue, one red, and one green. What color will the spot appear as?

White