DO NOW: EM journals in In Box. Then…Using appropriate vocab terms, please explain exactly what is going on in this photo. Does light change media? Speed up? slow down? Bend? Refract? BE COMPLETE!

Q & A Walk• Participate in the Walk or 5k and get +3 on your

final exam• Bring me your race bib next week and/or

registration bag to claim your points. • For info email: rua@robbinsville.k12.nj.us• Entry fee: $20 before June 8 ($18 for USATF

Members and students 14 and under), $25 on race day, $18 fitness walk

• Give Ms. Rua your registration form and fee. • Make Checks Payable to: Robbinsville High School• Information on the RHS website

Speed of light…

• Is ‘c’ in a vacuum• Is slower in air• Slower still in water• And even slower in glass• Looking at this picture, you have A LOT of

changing media, and therefore changing speeds.

• As light slows down, it ‘bends’ (refraction)

Refraction occurs when the average speed of light changes in going from one transparent medium to another. o We can understand this by considering the action of a pair of toy

cartwheels connected to an axle as the wheels roll gently downhill from a smooth sidewalk onto a grass lawn.

o If the wheels meet the grass at some angle, they will be deflected from their straight-line course. The direction of the rolling wheels is shown by the dashed line.

o Note that on meeting the lawn, where the wheels roll more slowly owing to interaction with the grass, the left wheel (YOUR left) slows down first. This is because it meets the grass while the right wheel (YOUR right) is still on the smooth sidewalk.

o The faster-moving right wheel tends to pivot about the slower-moving left wheel because during the same time interval, the right wheel travels farther than the left one.

• Light from is refracted through the sides of the thick glass - making the glass appear thinner than it is. The eye is used to seeing in straight lines, and perceives the root beer to be at the outer edge of the glass

That frosty mug full of A&W root beer seems to drain so quickly. What seems like a lot of root beer is actually a lot of glass. The deception is uncovered when the root beer mug is submerged in water. When looking at the mug above the water level, there appears to be a lot of root beer. But when looking at the mug below the water level, one observes the truth; the water surrounding the glass minimizes the effect of refraction and reveals the large quantity of glass. We've been deceived! 

That frosty mug full of A&W root beer seems to empty so quickly. What seems like a lot of root beer is actually a lot of glass. The deception is uncovered when the root beer mug is submerged in water. When looking at the mug above the water level, there appears to be a lot of root beer. But when looking at the mug below the water level, one observes the truth; the water surrounding the glass minimizes the effect of refraction and reveals the large quantity of glass. We've been deceived! Can you think of other products that may use this ‘physics’ illusion to make you think you are getting more product than you actually are?

• From yesterday’s exit:

(light slows down at water – it ‘bends’ and the image appears to be closer… this explains quarter, too!)

• Make correction/ additions

changes… questions?

• To explain prism, you must understand that high frequency light (violet) travels more slowly through glass than low frequency light (red)

Today’s Demos• Same as last class:

Demo Name

What did you SEE happening (words/picture)

Do Now – why do you THINK it was happening

Exit – what ACTUALLY happened?

Big MirrorsLight TubeMirage

Luminous vs. Illuminated

• What’s the difference? DISCUSS• Conclusions? • Luminous: emits its own light, light source,

shines, etc.– Examples?

• Illuminated: lit up because other light is shining on it, does not emit its own light, does not shine on its own, etc.– Examples?

So…is Rihanna a physics genius?

• Does ‘shine bright like a diamond’ make ‘physics’ sense? DISCUSS

• Thoughts?

So why are diamonds so sparkly?

(Or any reflective surface!)

• Critical angle - the angle of incidence above which total internal reflection occurs (in other words, at an angle LARGER THAN the critical angle, you observe total internal reflection – TIR)

• TIR only takes place when both of the following two conditions are met:– a light ray is in the more dense medium and

approaching the less dense medium.– the angle of incidence for the light ray is greater

than the critical angle (as mentioned above)

• You can observe total internal reflection when swimming:

• Or with ‘fiber optics’

• You can observe total internal reflection when swimming:

• Or with ‘fiber optics’

• Or with diamonds

Goals

1. See teacher to check in on any previous POGILS (they should be done and checked by the end of class)

2. Finish your FINAL POGIL of the school year! 3. Prep for your quest next class!4. Fill out exit slip and turn in NEXT CLASS – You will take your questNEXT WEEK – you will get your quest back and have

all of next week’s physics classes to prep for finals (study, work on cheat sheet, complete study guide this will be posted on my website this week for you to print)