On Target? Do this on your Warm Up worksheet!

No warm up today-get out your lab notebook and turn to your review table!

For today . . .1. Warmup2. Review

Fill this out in you lab notebook with your group:Activity Properties (Big

Ideas!)Significance to Astronomy

Stellar Parallax and finger model

Slinky Lab

EM Waves in Space and Cell Phones

Watt’s Up?

Starburst Graphing and Inverse Square Law

Star Spectra and Intensity Graphs

REVIEW ANALYSIS1. The Sun is a yellow-white star .

What range of surface temperatures would you expect on the Sun?

2. Spectral analysis of a star reveals that its light has a peak intensity at a wavelength of 640nm. Sketch a graph of the spectrum from this star and describe it’s temperature and color.

ANALYSIS: On the back1. Spectral analysis of a star reveals

that its light has a peak intensity at a wavelength of 640nm. Sketch a graph of the spectrum from this star and describe it’s temperature and color.

REVIEW ANALYSIS

A star has a peak intensity at 640 nm. What color is it? What temperature is it?

Formula: T (K) = 2.9 X 10 6

Peak wavelength

REVIEW ANALYSIS• Explain to your neighbor what is happening in this

picture! Why does the yellow star appear to change positions? Why does the yellow star appear to move more than the other stars in the photo?

I have two stars. Star A is 4.36 light-years (ly) from Earth, while Star B is 4.22 ly from Earth. When viewed from Earth in June, and again, in December, which star appears to shift the greatest distance compared to very distant background stars? EXPLAIN WHY. (1 light year = 9.5 trillion kilometers!)

REVIEW ANALYSIS

Parts of a Wave-Draw and label wavelength, frequency, and amplitude

Objective: I can describe the parts of a wave and label these parts on a drawing of a wave

Frequency of a Wave

What did we find?• Changing the wavelength, frequency, and

amplitude does not change the speed of the wave

• Changing the medium that the wave travels through does.• Only the material through which the wave travels (the

medium) affects the speed of a wave-changing the tension of the slinky!

Objective: I can test what variables change the speed of a wave and summarize class data for how wave speed changes.

• You and your best friend are having a race from the Sun to the Earth.• You are riding a red wave. Your bff is riding a blue wave.

Who will win the race? Explain why!“I think that… because…”

Speed of a Wave

• WHAT WE KNOW:Speed = distance/time

• But what if we don’t have a fast enough stop watch?

Speed = wavelength * frequency• c = λ * ν

Why do we see COLOR?

Read: EM Waves in Space-Rainbows From Outer Space (p. 481 – 484)

Answer the Following Questions in your Lab Notebook:• What type of wave travels through space, carries energy, and

is a type of radiation? • Visible light is an example of _______________ waves, also

called EM ________.• The speed of light is ________ at _________m/s.• What is the equation that relates speed, wavelength and

frequency?• At a constant speed, when the _________ of a wave increases,

the wavelength __________.• All waves in the EM spectrum vary in ____________ and

__________ but have the same ___________, the _______ of ________.

How do cellphones work? Voice

Electrical signal

(microphone)

EM wave (antenna)

Frequency adjustment

and matching with tower

Other phone

antenna

Converted to

electrical

Converted to voice

Why are some stars brighter than other stars?

Why do some stars look brighter than others?• Why is the sun the brightest star we can see?• It’s closest to us

• Is the sun the brightest star in the universe?• NO! Polaris (the north star) is 2200 times brighter

• Does that mean stars closer to us are always brighter?• NO! Polaris (the north star) is 433ly away but Proxima

Centauri is 4.2ly away. We can’t even see Proxima Centauri without a telescope because it’s so dim.

I can explain why some stars look brighter than others.

Why does Stellar Parallax not work for all stars?• Some stars are too far away (shift is so small, it is

not noticeable or there aren’t enough background stars for good comparison

• Apparent Brightness and Luminosity are used for these stars.

Inverse Square for light• What is the change in apparent brightness of a star if

you move twice the distance?

Answer In Your Lab Notebook!• If the distance from the source of energy increases 4

times, what happens to the apparent brightness, provided the luminosity remains the same?

*Remember your inverse square law equation!d=distance to the star, b=the apparent brightness of the starL=the luminosity of the star.

How do we know luminosity?Several different ways . . .

Read pg 498 and answer these questions in your lab notebook:• To find the distance to a star using the inverse square

law, what 2 things do you need to know?• How would scientists use the inverse square law to find

the luminosity of a nearby star?• If the distance to star A is 10 times greater than the

distance to star B, and the two stars have the same luminosity, how would their apparent brightness compare?