Warm Up

1. What kind of electromagnetic radiation has a wavelength of 3.0 m? What is its frequency?

2. What is the wavelength of light that has a frequency of 5.88x1014 Hz? What color is it?

3. What are the primary colors by addition? Subtraction?

4. What is the difference between color by addition and color by subtraction?

Reflection

• Reflection occurs when a wave strikes an object and bounces off of it

Mirror

Light

Reflection

• Reflection occurs when a wave strikes an object and bounces off of it

Mirror

Light

The angle of reflection must equal the angle of incidence

LAW OF REFLECTION

• The law of reflection says that light reflects (bounces) off of an object at the same angle at which the light hits it.

Examples of Reflection

• Light bounces off a mirror

• Bats use echolocation (sound waves bounce off of other objects)

REFLECTION EXAMPLE #2

Tinted windows on a car

•Tinted windows make it cooler inside cars by reflecting light away from the window.

• Reflection keeps heat out!• What wave carries heat that we

learned about from the EM spectrum?

Mirror

Mirror

Mirror

Two Types of Reflection

Flat surfaces reflect perfectly!

Rough surfaces reflect all over the place!

Refraction

• Refraction is the bending of a wave caused by the change in its speed as it moves from one medium to another

– What are some mediums that waves travel through?

– Does light need a medium to travel?

Liquids, Air, Solids

NO! It can travel through SPACE!

New Vocabulary

• Opaque- not able to be seen through

• Transparent- see through

When does it reflect/refract?• If an object is opaque, the light will reflect

because light cannot pass through a solid object.– Mirror– A book

• If an object is transparent, the light will refract because light can pass through the object.– Water– Prism

Refraction of Light in Water

• Light travels faster in air than in water– (water is more dense than the air…same goes for

glass or any other medium more dense than air)

• Because of this difference in speed, refraction causes underwater objects to appear closer to the surface than they really are

Refraction (Slowing Down)

• When a wave passes into a medium that makes it slow down, the wave will bend toward the normal

Air

Water

Refraction (Slowing Down)

• When a wave passes into a medium that makes it slow down, the wave will bend toward the normal

Air

Water

Refraction (Speeding Up)

• When a wave passes into a medium that makes it speed up, the wave will away from the normal

Air

Water

Refraction (Speeding Up)

• When a wave passes into a medium that makes it speed up, the wave will away from the normal

Air

Water