Project 3
pdf
keyboard_arrow_up
School
City Colleges of Chicago, Harry S Truman College *
*We aren’t endorsed by this school
Course
201
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
7
Uploaded by ChiefMoon10511
Name/s: Emmanuel Pena
PROJECT 3 (SLO8, SLO9)
Due: 10/22/2023
Aim
: (i) To understand thermal radiation spectrum and how temperature and peak wavelength
are related; (ii) To study how stellar spectrum and stellar radius affect luminosity of a star.
General Instruction
: To be able to successfully complete this project, you must be able to do a
screen capture from your device, able to copy-and-paste the image into this document, and do
proper cropping and resizing of the image for suitable presentation.
Part A
:
For this part, you will using this web app:
https://phet.colorado.edu/sims/html/blackbody-spectrum/latest/blackbody-spectrum_en.html
You may have heard the commonly-
used expression of something being “
red hot
” and
something being “
ice-blue cold
”. The color red has often been associated with something very
hot while the color blue is thought to represent something very cold.
But is this really true?
Your task is to verify or falsify this notion by examining the thermal radiation spectrum given off
when something is heated. This radiation spectrum is known as the “blackbody spectrum”.
1.
Open the web app given above. Check the box that says “Graph Values”.
2.
On the right side of the screen, you will see a thermometer. The triangular marker can
slide up and down to vary the temperature. Click and drag the marker to change the
temperature and see what happens.
3.
Look at the star inside the circle above the graph. Notice that the color changes as you
slide the thermometer marker up and down.
4.
Slide the thermometer marker until you see an
orange-red
color in the star. You do not
have to be precise since the color depends on how your device’s display has been
calibrated.
5.
Adjust the scales on the vertical and horizontal axes of the graph so that you see a clear
curve.
6.
(2 points) Write down the temperature reading and the peak wavelength as given on
the screen.
Please do not forget to include the units
.
The temperature is 2050k with a wavelength of 1.414(Um) and a power density of .047
Temperature:2050k
Peak wavelength: 1.414
7.
(2 points) Do a screen capture and paste the screen image here. Please resize and crop
the image to include only the relevant of the web app (full graph, star color, and
thermometer).
8.
(4 points) Repeat Task 4-7, but this time, slide the thermometer marker until you see a
blueish
color in the star. Write down the temperature and peak wavelength, and paste
your screen capture here.
Temperature:11000k
Peak wavelength: 0.263
9.
(2 points) Reexamine the original issue of “
red hot
” and “
ice-blue cold
”. Using what you
have seen so far using this app, verify or falsify this notion with a clear explanation.
Normally cold is associated with low temperatures that are freezing but, on this thing, the
higher temperature was cold and blue and the lower one was red hot
Part B
:
For this part, you will be using this web app:
https://astro.unl.edu/classaction/animations/stellarprops/stellarlum.html
The task here is to
find two additional stars
that have the
same luminosity
as the original star,
but one with a HIGHER temperature, while the other with a LOWER temperature, than the
original star. In the process, you will learn that luminosity depends on the temperature of the
star and the size of the star, and that stars of di
fferent temperature and “color” may have the
same luminosity if they have the right size.
In this app, the luminosity is given in two types of units, the SI unit of J/s (or Watts), and in solar
units, which is in multiple of the sun’s luminosity. The stellar radius is in multiples of the sun’s
radius.
As with Part A, perfect accuracy is not important. You only need to try your best to get to the
closest value that is asked for.
10.
(2 points) Using the sliders in the app, set your star to be spectral type F1 and stellar
radius to be 1.00 (i.e. the same size as our Sun). Call this
Star 1
. Do a screen capture and
paste the image here. Make sure it is properly sized and cropped. In addition, write in
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
the space provided the temperature and luminosity of the star in units of the Sun's
luminosity.
Temperature: 6885k
Luminosity (units of
L
sun
) : 1.95L
11.
(2 points)
Now, change the spectral type to a different type (different letter)
corresponding to a HIGHER TEMPERATURE than Star 1, and adjust the stellar radius until
you get a luminosity as close as you can to what you obtained in #10. Call this
Star 2
.
When you find the settings that you are happy with, record the temperature and
luminosity once again. Do a screen capture and paste the image here.
Temperature :
7930k
Luminosity (units of
L
sun
) : 1.96
Radius :
0.76
12.
(2 points) Repeat Task #11 with a star of a LOWER TEMPERTURE than Star 1. Call this
Star 3
. Paste your screen capture here.
Temperature : 6603
Luminosity (units of
L
sun
) : 1.99
Radius : 1.10
13.
(2 points) Arrange the stars in terms of its
size
, from
large to small
. Then arrange the
stars in terms of
temperature
, from
lowest to highest
.
Stars’ stellar radii, large to small:
star 3,star 1,star 2
Stars’ temperature, lowest to highest:
star 3, star 1, star 2
14.
(2 points) All three stars have approximately the same luminosity. What can you say
about the relationship between a star’s temperature and its size if its luminosity doesn’t
change?
The different temperature and size of a planet can be different but if it’s the
right set of temp and size for that temperature then they can all give off the same
amount of luminosity.
Part C (Extra Credit):
In the dark, we can’t
see anything, and this makes us draw the conclusion that it is because we
and everything else around us do not emit light. Is this claim true? What if what is meant by
“light” is the electromagnetic spectrum and not just the visible range of the electroma
gnetic
spectrum?
To tackle this question, let’s consider whether a human being emits any electromagnetic
radiation.
15.
(1 point) Human body has a temperature of approximately 37° Celsius. What is this
temperature in Kelvin?
T
body
(Kelvin) = 310k
16.
Use the web app in Part A and set the thermometer slider to approximately that temp.
Because the temperature scale isn’t exact and of limited range, you may set the
temperature close to the actual value.
17.
(1 point) Adjust the scaling so that you have a reasonable display of the curve. Once you
have a graph that you are happy with, do a screen capture and paste it here. Remember
to resize and crop if necessary. Write down the peak wavelength shown on the graph
(do not forget units).
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Peak wavelength: 1000rm
18.
(2 points) From your graph, it is obvious that a human body emits electromagnetic
radiation. So why are we invisible to each other in the dark?
All human beings give off heat from our bodies that are detectable by things that detect a
things body radiation. The only reason we cannot see eachother in the dark though is because
without a sense of light to refract into our eyes then we lose that sense of sight since no light
wavelengths refract into our eyes.