Light Absorption

Interaction of Waves with Matter

• Absorption is the transfer of energy by a wave to the medium through which it

  travels.

• One factor that affects the amount of energy absorbed is the wave in which a

  wave moves.

• All materials absorb electromagnetic waves.

• Transmission is the passage of light through an object.

• Reflection is the bouncing of a wave off a surface.

• Objects that reflect all visible light appear white.

• Objects that do not reflect any visible light appear black.

The Law of Reflection

• All types of waves can be reflected when they hit a surface.

• The angle at which a wave hits a surface is the same angle at which it bounces off

  the surface.

• The normal is an imaginary line that is perpendicular to a surface.

• The angle of incidence is equal to the angle between the normal and an

  incoming wave.

• The angle of reflection is equal to the angle between the normal and an outgoing wave.

• The angle of incidence and the angle of reflection are equal. This rule is called the law of reflection.

Refraction

• Refraction occurs when a wave changes direction because its speed changes.

• The greater the change in speed is, the more the wave changes direction.

Reflection

In reflection, waves meet a solid barrier and bounce back. For example, an echo occurs when a sound wave meets a wall and bounces back to the source of the sound.

Refraction

In refraction, waves move from one medium to another and bend, or refract. An example is a glass of water with a straw. Where the straw passes into the water, it looks broken. But the break is an illusion caused by refraction of light waves as they pass from air to water.

White vs. Black objects

Multiple Choice

What light property is observed in the picture?

• reflection

• transmission

• refraction

• opaque

Multiple Choice

Which property of an object refers to allowing all light to transmit through it?

• transparent

• translucent

• opaque

Refraction and Lenses

What Happens When Light Hits an Object?

What Determines the Type of Image Formed by a Lens?

What happens when light hits an object?

• Reflection

• Refraction

• Absorption

Reflection

• Occurs when light bounces off of an object

• Regular & Diffuse Reflections

• The colors we perceive are those that are reflected off of an object.

Refraction

• the bending of light as it changes speed

• some mediums cause light to bend more than others

• index of refraction: a measure of how much a light ray bends when it enters a specific medium

Absorption

• light waves are absorbed by an object

• We only see the colors that are NOT absorbed by that object.

Multiple Choice

What are three things that can happen when light hits an object?

• Regular, Diffuse, Obtuse

• Reflection, Refraction, and Absorption

• Concave, Convex, Plane

Multiple Choice

Which word best describes what happens to light when it "refracts"?

• stops

• bends

Multiple Choice

We do not see the colors that are absorbed, only those that are reflected off of an object.

• True

• False

Types of lenses

• Concave Lens

• Convex Lens

The Human Eye

• Retina: thin layer of cells that line the back of the eye

• Lens: convex shape, bends light to form an image on the retina

• pupil: the muscle that contracts when exposed to sunlight

• Iris: the color part of the eye

• Cornea: the protective outer layer

Multiple Choice

What do we call the back of the eye where images are projected as light?

• pupil

• retina

• iris

• cornea

Multiple Choice

What is the part of the eye that bends light so that an image can be projected onto the retina?

• optic nerve

• lens

• pupil

Multiple Choice

What do we call the muscle in the eye that contracts in sunlight?

• retina

• lens

• pupil

Multiple Choice

What is the protective layer on the outer eye called?

• Cornea

• lens

• pupil

Multiple Choice

According to Dutch scientist Christiaan Huygens, what was light made of?

• atoms

• particles

• waves

• electrons

Multiple Choice

Isaac Newton believed that light was made of

• waves

• particles

• dust

• gravity

Multiple Choice

What happens when light from the Sun passes through any type of matter?

• The light slows down.

• The light speeds up.

• Most of the light is absorbed.

• Most of the light is reflected.

Multiple Choice

Lisa sees the image below as she researches the behavior of light.

Which behavior is the spoon in the top image most likely being used to illustrate?

• refraction

• absorption

• reflection

• bounce

Multiple Choice

Which object is least likely to allow light to pass through it?

• a pair of eyeglasses

• a clear water bottle

• a car windshield

• a tree trunk

Multiple Choice

The diagram shows light interacting with an object.

Which object is the light most likely striking?

• a window

• a mirror

• a plaster wall

• a steel beam

Multiple Choice

Which statement best explains a difference between the interaction of light with clear glass and the interaction of light with silver metal?

• Light slows down when it interacts with glass but not when it interacts with metal.

• Light slows down when it interacts with metal but not when it interacts with glass.

• Most of the light passes through glass but none of the light passes through metal.

• Most of the light is absorbed by glass but none of the light is absorbed by metal.

Multiple Choice

Carla did an experiment by placing a piece of smooth, clear glass and a piece of smooth, black stone under a lamp for twenty minutes. Which prediction will most likely be supported by Carla’s experimental results?

• The glass will feel warmer than the stone after twenty minutes.

• The stone will feel warmer than the glass after twenty minutes.

• The glass will reflect all of the light after twenty minutes.

• The stone will reflect all of the light after twenty minutes.

Multiple Choice

Which object absorbs the most visible light?

• a clear bowl

• a white rock

• a black t-shirt

• a red apple

Multiple Choice

Allowing light to pass through so that objects behind can be clearly or distinctly seen.

• Transmit

• Transparent

• Refract

• Reflection

Multiple Choice

Any physcial substance through which energy can be transferred

• Light

• Medium

• Diverge

• Converge

Multiple Choice

The bouncing back of a ray of light, sound or heat when the ray hits a surface that it does not go through.

• Reflection

• Refraction

• Absorption

• Transparent

Multiple Choice

The transformation of radiant (light) power to another type of energy, usually heat, by interactions with matter

• Reflection

• Refraction

• Absorption

• Transparent

Multiple Choice

The bending of an energy wave as it enters a new medium at an angle.

• Reflection

• Absorption

• Transmission

• Refraction

Multiple Choice

Curving Inward. Curves toward incoming light.

• Concave

• Convex

• Refract

• Reflect

Multiple Choice

Curving outward. Curves away from incoming light.

• Refraction

• Reflection

• Concave

• Convex

Multiple Choice

Energy that can be sensed by the eye.

• Heat

• Light

• Electrical

• Sound

Multiple Choice

To pass through a substance or object without being absorbed.

• Reflection

• Absorption

• Transmit

• Transparent

Multiple Choice

Light bouncing off a mirror is an example of...

• Refraction
• Reflection

Multiple Choice

When light hits an area and bounces back it is called:

• echo

• refraction

• reflection

• absorbing

Multiple Choice

Light is a form of

• energy

• wave

• ray

• prism

Multiple Choice

The bending of light as it passes from one medium to the other is

• refraction

• reflection

• translucent

Multiple Choice

The bouncing of light off a surface

• refraction

• translucent

• opaque

• reflection

Multiple Choice

not letting light pass through

• opaque

• translucent

• transparent

• frequency

Multiple Choice

letting some light pass through

• opaque

• translucent

• transparent

• reflection

Multiple Choice

Reflection is when light...

• Bends

• Bounces

• Absorbs

• transmits

Multiple Choice

Refraction is when light...

• Bounces

• Transmits

• Bends

• Absorbs

Multiple Choice

___________ travels in a straight line until something changes its path

• Medium

• Refract

• Reflect

• Light

Multiple Choice

What is happening in this picture?

• Reflection

• Refraction

Multiple Choice

What is happening in this picture?

• Reflection

• Refraction

Multiple Choice

A student placed a pencil in a cup of water.  The pencil appears broken because light-

• always travels in a straight line
• bends when it passes through water
• makes the water in the glass evaporate
• reflects the pencil on the water's surface

Multiple Choice

The bouncing of light off an object

• basketball

• refraction

• reflection

• echo