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HW: U6-12 (green)

Next Test: Exam 6 on 2/15

Why it matters in LIFE:

Part of being a

functional human

being is being able to

understand what’s

happening in the world

around you!

Why it matters in THIS CLASS: Our Goal = 80%

Mastering today’s lesson (focused

participation, asking questions, etc)

is the first brick that will help us

reach our goal for this unit, and

eventually for the year

By the end of today, IWBAT…Describe reflection and refraction of

waves

Calculate angle of refraction using

Snell’s Law

TEKS:

(F) design, construct, and calculate

in terms of current through, potential

difference across, resistance of, and

power used by electric circuit

elements connected in both series

and parallel combinations;

Topic:

Reflection,

Refraction &

Snell’s Law

By the end of today, IWBAT…

Use RHRs to calculate and

determine the direction of

magnetic force.

Bouncing of waves off a surface or medium.

REFLECTION

REFLECTIONAngle of incidence = Angle of reflection

WHAT IS THE ANGLE OF REFLECTION IF

THE ANGLE OF INCIDENCE IS 35

DEGREES FROM THE NORMAL?

WHAT IS THE ANGLE OF REFLECTION

GIVEN THE ANGLE BELOW?

42

degrees

Refraction-The bending of a wave due to a change in medium (or substance).

θ1

θ2

Boundary Line

• Boundary Line

INDEX OF REFRACTION, n , (no units!)

• The index of refraction, n, is a constant associated

with a particular material.

• The higher n is, the more light bends and slows down.

n = index of refraction (no units)

c = speed of light (m/s)

v = velocity of the wave in the current material (m/s)

Each medium has its own index of refraction

INDEX OF REFRACTION PRACTICE

1.A physicist measures the speed of an electromagnetic wave as 2.6*108 m/s in a medium. What is the index of refraction of the medium?

Snell’s LawThe relationship between the angles of incidence and angle of refraction of two media.

n1 = index of refraction of first medium

θ1= angle of incidence

n2 = index of refraction of the second medium

θ2= angle of refraction

n1sinθ1 = n2sinθ2

Snell’s Law Practice1. Light travels from a region of air (n=1.00029) to a region of lead (n=2.6) making an angle of 40˚.

a. Calculate the angle of refraction.

b. Predict whether the light will move faster or slower in the lead than in air. Justify your answer.

c. How fast will the light be traveling in the lead?

Snell’s Law Practice2. An incident ray in air (n=1.00029) is approaching the boundary with an unknown material at an angle of incidence of 61.6°. The angle of refraction is 41.4°. Determine the index of refraction of the unknown material.

Snell’s Law Practice3. An incident ray in air (n=1.00029) is approaching the boundary with glass (n = 1.52) at an angle of incidence of 32.5°. Calculate the angle of refraction.

Procedure for IP time:

1) Silent work time

2) Try and solve without notes first!

Hierarchy of who to ask

1) Your brain

2) Your notes

3) Your partner (quiet whisper)

4) Ms. Kelly

INDEPENDENT PRACTICE!

EXIT TICKET (4 MIN)1. What is this image an example

of? How do you know?

2. Light travels from air (n=1.00) into an optical fiber with an

index of refraction of 1.44. If the angle of incidence on the

end of the fiber is 22o, what is the angle of refraction inside

the fiber?

3. What is its speed in the fiber?

EXIT TICKET (4 MIN)1. What is this image an example

of? How do you know?

Reflection! The angle of incidence is equal to the angle of

reflection and the waves are “bouncing” off the surface.

2. Light travels from air (n=1.00) into an optical fiber with an

index of refraction of 1.44. If the angle of incidence on the

end of the fiber is 22o, what is the angle of refraction inside

the fiber?

θ2 =15.08°

3. What is its speed in the fiber? v = 208,333,333.3 m/s

CLOSURE

In complete sentences:

• 3 things you learned

• 2 things you liked

• 1 question you still have