Pop Quiz TimeHit 1, hit 2, hit 3 your in!

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Please grab your calculatorWhat is the:Sin 30o

.5 Sin 45o

.71Sin 22o

.37Sin 35o / sin 55o

.7

Physics Journals

Date Table of contents page #

Semester 21/7 Conservation of Momentum ?1/14 Sounds in Vibrating Strings ?1/21 Making Waves ?1/28 Sounds in Strings Revisited ?2/3 Sounds From Vibrating Air ?2/11 Shadows and Color Addition ?2/13 Reflected Light ?2/19 Curved Mirrors ?2/26 Refraction of Light ?

Homework:Due Tuesday /Wednesday

Read PT pg 561-562CU pg 562 #1PTG pg 565 #1,3,6,7,8

Honors include:#9,10

CLO:SW explore refraction, Observing and then writing an explanation as to what is meant by “Index of Refraction” and what happens as light travels from a less optically dense medium to a more optically dense medium.

Section #8Refraction of Light

pg 558,

Materials:#1 -7-acrylic block-protractor-pencil-calculator-laser-straight edge

#1-6:What I want to see

Copy data table pg 559Skip the graphing part but calculate the ratio of the

sin of angle Incidence to the sin of the angle of refraction for each trial

Finish this statement:The ratio of the sin of angle of incidence to the sin of angle of refraction was the same or different for all three trials.

Do now:1. A flagpole is casting a shadow as shown in the diagram. Which of the following would make the length of the shadow shorter?a) Increasing the height of the flagpole.b) Moving the Sun in the vertical direction “up”.c) Making the Sun brighter.d) The Sun in the vertical direction “down”.2. The diagram below shows a light ray striking a concave mirror parallel to the principal axis. Point C is the center of curvature of the mirror, and point F is the principal focus. The light ray will reflect through which point?

3. If an image distance is negative, is it real or virtual?4. If an object height is – is it real or virtual?

Let’s look at the data you gathered last week from 4 groups

3groups:Angle of incidence Angle or refraction1) 39o 25o

2) 23o 15o

3) 32o 20o

4) 45o 27o

For each data set, divide the sini by the sinr:

sini

sinr

CLO:SW define refraction, Dispersion, and index of refraction, and Snell’s law. Being able to identify, write out and solve problems involving the application of Snell’s Law.

The ratio of the sin of angle of incidence to the sin of angle of refraction was the same or different for all three trials.Crucial Physics: How does light refract when going from less to more optically dense media?

-car in mud scenario-camping at a lake scenario

Let’s take some notes!

Refraction

Refraction

Dispersion of Light

Index of RefractionDefined:Examples:Visual:

Law of Refraction(Snell’s Law)

Defined:Equation:

Refraction

Refraction

the change in direction of a propagating wave (light or sound) when passing from

one medium to another

Let’s look at a prism, why do we see all the colors?

Shoulder partner share-out

Let’s see what Bill Nye says (first 1.05-2.20 min)http://www.youtube.com/watch?v=gtgBHsSzCPE&feature=related

DispersionROYGBIV

Higher frequencies of white light refract more

Index of Refraction

nDefined:

“n” A transparent materials ability to bend lightExamples:

Air or vacuum n=1.0Acrylic n= 1.5Water n= 1.3Diamond n=2.4

Visual:

Visual: n=1.0 i

n=1.3

r

Concept Check:Light enters the following substances at an angle, what happens to the light as it goes from one substance to another.

n= 1.0

n= 1.0

n= 1.7

n= 1.7

n= 1.0

n= 1.2

n= 1.5

.

n= 1.0

n= 1.0

n= 1.7

n= 1.7

n= 1.0

n= 1.2

n= 1.5

Law of Refraction(Snell’s Law)

Defined:

The index of refraction of a material is equal to the ratio of the sin of the angle of incidence to the sin of the angle of refraction.

Equation:

n= sini

sinr

Take a break, and put down your pencil

ni sini = nr sinr

My favorite equation to say out loud

Snell’s Law w/ a bit more detailni sini = nr sinr

ni = Index of refraction of incident mediumnr = Index of refraction of substance light enterssini = sin of the angle of incidencesinr =sin of the angle of refraction

(if the incident medium is air ni is 1)Therefore:

nr = sini / sinr So, as light travels from one medium to another we use Snell’s law:

ni sini = nr sinr

Law of Refraction(Snell’s Law)

Defined:

The index of refraction of a material is equal to the ratio of the sin of the angle of incidence to the sin of the angle of refraction.

Equation:

In a vacuum or air

n= sini

sinr

or

ni sini = nr sinr

What happens if two objects have the same index of refraction?

Pyrex and Baby Oil

Grab your calculators please

1. In the picture below, the incident beam from air (n=1) has an angle of incidence of 30o

The refracted ray has an angle 22o to the normal.What is the index of refraction for the material the light is entering?

1.33

2.A ray of light is incident at an angle of 40.0o upon the surface of a diamond (n=2.4). What is the angle of refraction?

15.5o

3. A block of material is submerged in water (n=1.33) light in the water is incident on the block at an angle of 31o to the normal. The angle of refraction in the block is 27o.

What is the materials index of refraction?

1.47

Homework:Due next class

Read PT pg 561-562CU pg 562 #1PTG pg 565 #1,3,6,7,8

Honors include:#9,10

Do Now:1. A student shines a laser into a fish tank as shown in the following diagram. On which of the fish in the diagram would the laser beam shine?

2. An object is placed at a distance greater than the center of curvature from a Concave mirror. Give three properties of the image that is formed.

3. If you want to double the speed of a roller coaster at the base of the 1st hill, how much higher must you make the hill?

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The following people missed the quiz last Thursday (shadows and reflection):EmmaConnorMiaVinnieAlejandra HJalitzaAndresVictoriaMonica

refractive indices

Vacuum 1 (by definition)

Air (at 0 °C, 1 atm) 1.0002926

Water ice 1.31

Water (at 20 °C) 1.333

Glass 1.47-1.52

Acrylic 1.49-1.50

Sapphire 1.762–1.778

Cubic zirconia 2.15 - 2.18

Diamond 2.419

Some common refractive indices (n):

Gather the data and calculate the index of refraction for Water and crown glass.

SW explore Total Internal Reflection, and apply a new equation to solving light refraction problems, demonstrating proficiency through “Practice Perfect”.

Another equation to find Index of Refraction!

nr = speed of light in a vacuum or air

speed of light in the material

nr = C / vr

Speed of light in a vacuum or air = 3.0 x 108 m/s

What is the speed of light in a diamond (n=2.4)?

Index of refractionand speed of light

Equation:

nsubstance = C

vsubstance

C= 3.0x108 m/s

1-2-4 problems:1. The speed of light in air is 3.0 x 108 m/s while the

speed of light in glass is 2.0 x 108 m/s what is the index of refraction of the glass?

1.5

2. A diamond has an index of refraction of 2.4, since you know the speed of light in air is 3.0 x 108 m/s, calculate the speed of light in a diamond.

1.25 x 108 m/s

Practice Perfect Snell’s Law

1. nr= 1.46

2. nr= 1.33

3. r= 35o4. r=51o5. r=28oA=62o B=58o C=32o D=53o

6. 1.57. Glass= 41.8o Diamond=24.6o

Collect HW

CLO:SW will explore total internal reflection of light, and observe what is meant by “critical angle”. Being able to define and diagram what happens when total internal reflection occurs.

Turn to page560

Materials needed: -Laser-Triangle prism

Do #7-9 15 minutes By the end of the activity, be able to answer the following:

-What is total internal reflection?-What is critical angle?

Critical angle and total internal reflectionhttp://www.youtube.com/watch?v=2kBOqfS0nmE&safety_mode=true&persist_safety_mode=1

Critical AngleExplained:When light goes from a more optically dense medium (incident medium) to a less optically dense medium (refractive medium) and makes an angle of refraction of 90o

Total InternalReflection

When the angle of refraction is greater than 90o

Let’s draw it in our notes:Three colored pencils and straight edge

Which ray is characteristic of what will happen?

Baby Oil and Pyrex?Gel Beads?

Penny in a bowlFiber optics

Explain (you cannot just say “refraction”

1.Why are the optical properties of diamonds different then that of glass?

2.Why does the straw appear broken in the glass of water?

3.How do you explain the mirage on the road?

Practice PerfectSnell’s Law

Grab a ruler

Draw the image formation for an object placed at the center of curvature for a concave mirror.