# ANSWERS TO STOP & THINK AND REFLECT & CONNECT

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ANSWERS TO STOP & THINK AND REFLECT & CONNECT
Chapter 10 stars ANSWERS TO STOP & THINK AND REFLECT & CONNECT

Reflect and Connect: Star pictures Page 462

Reflect and Connect: Star pictures Answers Page 462
The changes observed is the result of the rotation of the Earth. Just as the Moon and the Sun seem to move across the sky, stars to the same, because the EARTH IS MOVING. Constellations seem to move because the Earth revolves around the Sun, and as such different groups of stars are brought into view as the seasons progress

Reflect and Connect: Stars at a glance Page 466
Why do you think your finger appears to shift in position when you look at it first with one eye and then the other? Compare the apparent shift of your finger at different distances. What did you notice about the shift when your finger was closer to and further away from your eye? To answer that question, complete the following sentence: As the distance from my eye to my finger increases…….. How might a similar process be useful to astronomers?

Reflect and Connect: Stars at a glance Answers Page 466
Looking with one eye and then the other is actually looking at the same object from 2 different positions. If you look at your finger from a different positron, your finger will shift with respect to the background. As the distance from my eye to my finger increases, the apparent shift decreases. As the distance from my eye to my finger decreases, the apparent shift increases. If your fingers represent a star that is much closer than the background stars. The line on the paper represents the backgrounds stars. Then fi astronomers could view these stars from 2 different locations (as with different eyes) they can determine the distance to these stars. There is a relationship between the distance from a nearby star to background distant stars and the apparent shift in position when viewed from different locations.

Reflect and Connect: Stellar Parallax Page 468;470
View a simulation of stellar parallax as directed by your teacher. Make sure you click and drag the red star closer and farther from Earth. How is your model with your finger and line similar to this simulation of stellar parallax? To answer that, draw a T-table in your science notebook to organize your responses to Questions 1a-c. Label the top of the T-table with 2 headings “My Model” and “Stellar Parallax Simulation”. What does your finger represent? What does the line represent? What do your eyes represent? Alpha Centauri, a nearby star is 4.36 (ly) from Earth, and Proxima Centauri 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 stars in the background? Explain. IF you are not familiar with light years READ “Monster Units” Both Alpha Centauri and Proxima Centauri are in the constellation Centaurus, the Centaur. How would you respond to the student who said that all stars in a constellation are the same distance from Earth?

Reflect and Connect: Stellar Parallax Answers Page 468;470
T-Table Proxima Centauri, is closer to Earth it would appear to shift the greatest distance when compared to the background stars. Similarly, Alpha Centauri, would shift less. This is because as a star’s distance from Earth increases, its parallax angle decreases, causing the shift in position to appear less. Stars in the same constellation are not all the same distance from Earth. Constellations are not actual features in space but only human made patterns from the stars we see at night My Model Stellar Parallax 1. Index finger Near Star Line Distant background stars Eyes Different locations of Earth in the sky

Reflect and Connect: Springing into action Page 474

Reflect and Connect: Springing into action Page 474 Continued
How does the speed of sound compare with the speed of light? Using the same method explained in Question 3, determine how much faster light waves travel compared to sound waves. Be sure to show your work. What features of thunderstorms help confirm your calculations in Question 4?

Reflect and Connect: Springing into action Answers Page 474
The type of material through which the wave travels (medium) affects the speed of the wave. Calculations: time = distance/speed time = 1.5 x 1011m 3 x 108 m/s. Then convert to minutes 500s x 1min = 8.3min 60s For example: if your wave has a speed of 10m/s, the ratio would be as follows So you can say that the speed of sound is 34 times faster than the speed of the wave = 500 s 340m/s 10 m/s =34

Reflect and Connect: Springing into action answers Page 474 Continued
Using the relationship 3 x 108 m/s = 880,000 340 m/s So you can say that the speed of light is 880,000 times faster than the speed of sound. When you see lightning from a storm it takes several seconds before you hear the thunder.

Imagine that you are creating a wave on a spring by shaking your hand from side to side. Without changing the distance your hand moves, you being shaking your hand faster and faster. What happens to the amplitude, frequency, wavelength, and speed of your wave? Waves are sent along a spring of fixed length. Explain how (or if) you could change the variables listed in figure Cite evidence for your answers from the activity. Copy the chart in figure to organize your response. Does a wave transfer matter, energy, or both? What is your evidence? Variable How to Change Evidence from activity Speed Frequency Amplitude Wavelength

Since distance hand moves doesn’t change; amplitude doesn’t change. Frequency and wavelength will change. Since you don’t change springs the speed stays the same. T-Table. Remember the tape? This represents that matter was NOT transferred. Evidence supports that the tape returned to its original position while the ENERGY of the wave moved through the slinky. Variable How to Change Evidence from activity Speed You cannot change the speed unless you change the medium Changing the medium was the only way to change the speed Frequency Move hand up and down faster/slower When making waves as fast as you could Amplitude Can make amplitude bigger by moving hands at greater distances up and down When moving greater distance the amplitude increased Wavelength Must move up/down quickly to decrease and slowly to increase When you increased frequency the wavelength became shorter

If you add more total energy to a wave (as you did in Step 7), what happens to the The frequency gets higher or increases Wavelength gets shorter or decreases A wave moves 12m in 5 seconds. There are 6 complete waves produced in that distance and time. Using this information, complete the tasks and answer the following questions Calculate the speed using the equation: speed = distance/time 12m/ 5s = 2.4m/s. speed= λ x f to calculate speed another way. F= number of waves/second. 6 waves pass in 5 seconds. So the f = 1.2 Hz Now: 6 waves in 12 min; each wavelength must have a wavelength of 2m. Speed = wavelength x frequency Speed = 2m x 1.2Hz = 2.4 m/s They are the same

Which has the highest frequency? Which has the longest wavelength?
Reflect and connect: Part II Starlight- Cell Phone calls from outer space Page 487 What is the order of the 7 colors in the visible spectrum? Name them in order from longest wavelength to shortest wavelength. Using the EM spectrum (fig 10.21), consider X-rays and radio waves to answer the following questions: Which has the highest frequency? Which has the longest wavelength? Which has the greatest energy? Make a T-table with 2 columns, labeling the headings “Red Light” and “Blue Light”. In your table, indicate the differences, if any in the following: Wavelength Frequency Energy Speed

Reflect and connect: Part II Starlight- Cell Phone calls from outer space Page 487
Do cell phones use only EM waves in their operation? Think of the different steps in a cell phone conversation and think about the paths of all waves. Indicate in you answer all the steps you can think of and all the different types of waves involved. These activities were about waves and the fact that waves have similar properties whether they are sound waves, waves on a Slinky, or light waves. In a Reflect and Connect question in the Springing into Action! Activity, you imagined riding on a light wave from the Sun to Earth and calculated that your journey would take just over 8 minutes. Would it make any difference in time if you were riding a blue light wave versus a red light wave? Give evidence to support your answer.

ROYGBIV in order from longest to shortest wavelength
Reflect and connect: Part II Starlight- Cell Phone calls from outer space (Answers) Page 487 ROYGBIV in order from longest to shortest wavelength Significant: colors of the rainbow. The colors correspond to increasing frequencies and decreasing wavelengths of light from red-violet. Using the EM spectrum (fig 10.21), consider X-rays and radio waves to answer the following questions: X-Rays have the highest frequency Radio waves have much longer wavelengths than X-Rays X-rays have greater energy than radio waves Make a T-table with 2 columns, labeling the headings “Red Light” and “Blue Light”. In your table, indicate the differences, if any in the following: Red Light Blue Light Longer Wavelength Shorter Wavelength Lower Frequency Higher Frequency Lower Energy Higher Energy Equal speed 3 x 108 m/s

More involved than just EM waves zipping back and forth at 840MHz.
Reflect and connect: Part II Starlight- Cell Phone calls from outer space Page 487 Continued More involved than just EM waves zipping back and forth at 840MHz. Why? Eardrum cannot detect EM at that frequency Microwaves enter the cell phones, phones decode that signal and then recode the signal that it can be resent as sound waves to your ear Small speaker sends the sound waves to your ear at the speed of sound. Brain processes sound waves and decides upon a response Speak w/ vocal chords vibrating at certain frequencies Sound waves trigger a receiver in the phone which then translates the signal to a code in EM waves They are sent from the cell phone at the speed of light to a cell tower w/in a grid where the waves are relayed to the original caller Remember: that the speed of the wave is constant unless the medium thru which it travels changes properties. It doesn’t matter if you ride a blue wave or a red wave. However, a blue light wave would have a higher frequency and a shorter wavelength so it would “feel” shorter

Stop and Think: Part I Watt’s UP? Page 489: 491

Stop and Think: Part I Watt’s UP? Page 489: 491 (Answers)
The higher the wattage of the light bulb, the brighter it appears Yes. Show that if the lower wattage bulb were closer to the observer it appears brighter than the higher watt bulb Warnings are on lamps because using a bulb with a higher wattage could melt the lamp Your eyes and hands only receive part of the energy emitted from the bulb. If someone else was looking/feeling from the opposites side of the bulb they would feel another portion of the energy. If you move farther way you receive less energy. You saw in your teacher’s demo that the energy output of a light bulb is not always obvious when the light bulb is placed at different distances. You also felt the heat given off by the bulbs. Less heat if you move farther from the bulb Energy striking your hand increases as you move closer to the bulb and decreases as you move farther from the bulb

Stop and Think: Part I Watt’s UP? Page 489: 491
A friend see’s a very bright star in the constellation Orion and tells you that it is very bright because it is much closer to Earth than the dimmer stars. Obviously, this friend is not in your science class! Could this statement be true? Or are there other factors to consider? Write a short paragraph explaining a better way to describe the apparent brightness of this star. Why do astronomers need to know the apparent brightness and luminosity of stars? You learned in an earlier activity about how scientists use stellar parallax to determine distances to stars. Does this method work for all stars? Explain.

Stop and Think: Part I Watt’s UP? Page 489: 491 (Answers)
The higher the wattage of the light bulb, the brighter it appears Yes. Show that if the lower wattage bulb were closer to the observer it appears brighter than the higher watt bulb Warnings are on lamps because using a bulb with a higher wattage could melt the lamp Your eyes and hands only receive part of the energy emitted from the bulb. If someone else was looking/feeling from the opposites side of the bulb they would feel another portion of the energy. If you move farther way you receive less energy. You saw in your teacher’s demo that the energy output of a light bulb is not always obvious when the light bulb is placed at different distances. You also felt the heat given off by the bulbs. Less heat if you move farther from the bulb Energy striking your hand increases as you move closer to the bulb and decreases as you move farther from the bulb

Stop and Think: Part I Watt’s UP? Page 489: 491 continued
This very bright star could be closer but is not necessarily. The star could be the same distance from Earth as a dim star but be more powerful-have more watts. The star could be more distant than dimmer stars if the dimmer stars were much less powerful than the brighter, more distant star. Astronomers use the relationship between apparent brightness and luminosity of stars to determine their distance from Earth. No, parallax only works for nearby stars-stars with a few hundred ly. To find the distances to stars beyond the capabilities of stellar parallax, astronomers turn to apparent brightness and luminosity.

Stop and Think: Part II Starburst Page 497: 501
Create the T-Table (DIDN’T DO) If the distance from the source of energy increases 4 times, what happens to the apparent brightness, provided the luminosity stays the same What would happened to the flux or apparent brightness if the distance were cut in ½? In a previous analogy, apparent brightness and luminosity are compared to rain hitting a windshield and rain falling from the clouds. As with all analogies and models, there are strengths and weaknesses to the comparison. Make a T-table in your science notebook with the headings “Strengths” and “Weaknesses”. Think about how the analogy is a good comparison and list those as strengths. Also, consider how this analogy is not a good example and list those reasons as weaknesses. 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 2 stars have the same luminosity, how would their apparent brightness compare?

Stop and Think: Part II Starburst Page 497: 501
T-Table The flux decreases by a factor of 16. If the distance decreases by 1/2 , the flux increases by a factor of 4 T-Table You must know the apparent brightness (AB) and the luminosity (L) If star is nearby (use parallax). AB could be measured w/ a light meter and then luminosity can be calculated by: AB = L 4 x π x d2 The apparent brightness of Star B would be 100 times (102) brighter than Star A Strengths Weaknesses Rain hitting the windshield simulates flux, which is like brightness The rain from a cloud falls in one direction (down), a light travels in all directions We see the rain hitting our windshield & we see apparent brightness Rain is matter, light is energy Raindrops are particles, light acts like particles The amount of rain per square meter (flux) doesn’t change much, if any, with distance Clouds are point sources of light

Reflect and connect: Part III colorful characteristics Page 508
Describe what you can learn about stars by looking at their spectra. Give examples of what astronomers look for in spectra. The Sun is a yellow-white star. What range of surface temperatures would you expect from the Sun? Spectral analysis of a particular star reveals that its light has a peak in intensity at a wavelength of λ = 640nm. Draw a sketch graph of the spectrum from this star and describe its temperature and color.

Reflect and connect Page 508
In each activity in this chapter, you learned certain characteristic properties of stars and the info that scientists can lean from these properties. Make a chart in your notebook using the guide in fig Fill in the chart with the properties that were addressed in each activity and the significance of each property to astronomers you may look back in your book/notebook to compose your answers. Activity Property/properties Sig. to Astronomers Glance & Stellar Parallax Springing into Action! Much Ado about Waves Starlight: Cell Phone Calls from Outer Space Watts Up? Starburst Colorful Characteristics

Reflect and connect: Part III colorful characteristics Page 508 (answers)
Describe what you can learn about stars by looking at their spectra. Give examples of what astronomers look for in spectra. The Sun is a yellow-white star. What range of surface temperatures would you expect from the Sun? Spectral analysis of a particular star reveals that its light has a peak in intensity at a wavelength of λ = 640nm. Draw a sketch graph of the spectrum from this star and describe its temperature and color.

Reflect and connect Page 508 (Answers)
In each activity in this chapter, you learned certain characteristic properties of stars and the info that scientists can lean from these properties. Make a chart in your notebook using the guide in fig Fill in the chart with the properties that were addressed in each activity and the significance of each property to astronomers you may look back in your book/notebook to compose your answers. Activity Property/properties Sig. to Astronomers Glance & Stellar Parallax Springing into Action! Much Ado about Waves Starlight: Cell Phone Calls from Outer Space Watts Up? Starburst Colorful Characteristics

Reflect and connect: Putting it all together Page 511
From a star’s spectrum, astronomers can; Id the elements present in the star Notice the strength of the hydrogen lines Measure the wavelength emitted with the highest intensity Determine the surface temperature of stars based on the wavelength of greatest intensity Id the color of the star Classify the star based on surface temperature and absorption lines Astronomers look for absorption line spectra to determine the elements present. They measure relative intensities of the wavelengths to determine the surface temp. and color of the star Use Wien’s Law to answer this question. T range is from 5,000K to 6,000K Graphs

Reflect and connect Page 508
Activity Property/properties Sig. to Astronomers Glance & Stellar Parallax Apparent shift in position of the stars with respect to background stars when viewed from different perspectives Astronomers can determine the distances to nearby stars using parallax Springing into Action! Much Ado about Waves Speed, frequency, wavelength, and amplitude The speed of a wave is constant in constant medium. Waves transfer energy, not matter. Frequency of a wave and wavelength are inverse relationships Starlight: Cell Phone Calls from Outer Space Light as a form of EM radiation Astronomers use the formula c = f x λ to determine wavelength or frequency. Wavelength and frequency of EM radiation determine the properties of that radiation such as color. Info astronomers use to analyze stars comes in the form of EM radiation Watts Up? Apparent Brightness (AB), luminosity Astronomers use AB w/ a light meter and can determine luminosity of near stars using parallax. Distance to stars is important to know to compare AB and luminosity Starburst Inverse square law, Cepheid variable stars Astronomers can use the inverse square law and Leavitt’s work with Cepheid variable stars to determine luminosities and distances of stars too distant to use parallax Colorful Characteristics Spectra, intensity, color, wavelength, and temperature Astronomers use these properties of stars to determine such things such as elements that make up the star, the color of the star, and the temperature of the star T-Table.

Reflect and connect: Putting it all together Page 511
Even though there did not appear to be a relationship between distance and temperature, why is it important to know the distance to stars when trying to understand their characteristics? Recall that in Part I of the previous activity, you compared properties of distance, apparent brightness, and luminosity. You also felt the temperature of the air around different wattages of bulbs. What data could you have collected in Part I and plotted on a graph that would have resemble the data you used to make your HR diagram? One of the first things scientist do when they look at unfamiliar things is to classify them. Why would astronomers want to classify stars?

Reflect and connect: Putting it all together Page 511 (Answers)
Remember from earlier activities that a stars apparent brightness is related to its distance from Earth. If astronomers determine distance, they can factor it into their observations of star’s brightness. They can determine a star’s luminosity, or total power output. This is an inherent feature of the star that is independent of distance. Luminosity tells astronomers how much power a star produces and how large a star is. Remember that taking data on the wattage of the bulb and the temp at a specified distance from the bulb would give data similar to what you graphed for stars. Plotting this data would show similar relationships. These experiences w/ the light bulbs would model stars that would fall in the main sequence. Scientist classify things so they can determine patterns or relationships that exists between characteristics. Those with similar characteristics can be placed into groups. When groups overlap scientists can make predictions about relationships and test those predictions with new members of the groups. Scientists use relationships to develop ideas about how stars are born, live, and die.