Download Topic 3 Assignment - Science 9 Portfolio

Jordan Bannerman
Science 9
Unit 5: Space
Topic 3 - The Spectroscope:
New Meanings In Light
Spectral Lines
Isaac Newton passed a beam of light through a prism to produce a spectrum of
colors. If you pass the light through a narrow slit before sending it through a
prism (a spectroscope is a device that does this) the spectrum will be in more
detail. Joseph von Fraunhofer used a spectroscope to observe the spectrum
produced by the Sun. He noticed dark lines, called spectral lines, but didn’t
know what they meant. He found these spectral lines throughout the solar
system.
Spectroscopy: The Science of Colour
The significance of the spectral lines was discovered about 50 years later when
Kirschoff and Bunsen, two chemists used a spectroscope to observe various
chemicals when they were heated. They found some of the lines missing in some
of the chemicals. Each particular element had its own unique spectral lines. This
led to the science of spectroscopy – the study of spectra, as a part of chemistry.
They found that there were three types of spectra.
Spectroscopy for Astronomers
Astronomers refract the light from distant stars to determine what the star is
made of. Stars have dark bands in distinct sequences and thicknesses on their
spectra. Each element that is present in the star creates its own black-line
‘fingerprint’.
The spectra of the star are then compared to known spectra of elements to
determine the star’s composition. This is called spectral analysis. A spectrometer
is used to do this. By attaching spectroscopes to their telescopes, astronomers are
able to observe a star’s spectra, but because the distant stars are much dimmer
than our Sun, only some of the elements in the spectra can be identified. Those
that cannot be identified remain as
inferences, based on what astronomers
know about certain types of stars.
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The Doppler Effect
A change in the pitch (frequency) of sound waves because they are stretched or
squeezed is known as the Doppler effect. Changes in the sound waves can be
measured to determine how fast and in what direction a light-emitting object is
moving. The position of the dark bands is what shifts in the light waves of a
moving star.
The spectrum of an approaching star shows the
dark bands shifting to the blue end of the
spectrum, whereas, the shift is to the red part of
the spectrum if a star is moving away from the
Earth.
Remember:
Blue moving towards (cold you can touch)
Red moving away (HOT stay away)
The amount of shift indicates the speed at which the star is approaching or
moving away. There are also practical applications that use the Doppler effect.
Law enforcement officers detect the speed of an approaching vehicle by using
a radar gun, which sends out a radio signal and receives one back from the
vehicle. To determine the speed of the vehicle, the hand-held device records
the difference in the outgoing wavelength and incoming wavelength.
An Amazing Tool
The spectroscope is an amazing tool. Its application to astronomy has helped
astronomers determine the composition of distant stars
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Topic 3 Assignment
Vocabulary:
Spectrum- The distribution of energy emitted by a radiant source, as by an
incandescent body, arranged in order of wavelengths.
Spectral lines- An isolated bright or dark line in a spectrum produced by emission or
absorption of light of a single wavelength.
Spectroscopy- Study of spectra, especially experimental observation of optical
spectra.
Diffraction grating- A usually glass or polished metal surface having a large number
of very fine parallel grooves or slits and used to produce optical spectra by
diffraction of reflected or transmitted light.
Spectral analysis- Method of analyzing the chemical properties of matter from bands
in their visible spectrum
Doppler effect- Change in frequency of a wave for an observer moving relative to the
source of the wave
Red shifted- When an object is travelling away from you at the speed of light,
producing red light
Blue shifted- When an object is travelling towards you at the speed of light, emitting
a blue light
1. Describe how a spectroscope works.
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The small slit in the one end, allows a small amount of shaped light in, and
then as it passes through the eye piece, the colors break apart. This allows you
too see the spectroscope and the different elements your viewing.
2. If you heat a piece of wire until it glows, what type of spectrum should it
produce?
It will produce a continuous spectrum because the light is emitting from a hot
matter. If it was a gas, it wouldn’t be continuous.
3. What instrument would you use to find out what elements are in the
Sun’s atmosphere. How is this done?
You would use a spectroscope, because it tells you what is emitting light, and
what those things are, based on their pattern.
4. If a star’s light is red shifted what can astronomers conclude about the
movement of that star?
The star is travelling at the speed of light, in the opposite direction of them.
This will make the wavelengths longer.
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6. What is the Doppler effect? Give an example of it being used.
The Doppler affect proves how noises travelling towards you or away from
you change the differences in wavelengths.
7. Answer questions # 6 and 7 in the Topic 3 Review questions page 384.
Use the space below.
Analyzing Spectral Patterns
What to Do
Analyze the spectra below in order to answer the following questions.
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Questions
Use the space below, or a separate page, to
write
answers to the questions.
1. List the chemical elements in:
(a) Mystery Star 1
Helium and Hydrogen ___________
(b) Mystery Star 2
Helium, Hydrogen and Sodium____
(c) Mystery Star 3
Hydrogen and Calcium
2. (a) There is something strange about
Mystery
Star 4’s spectrum. What chemical is
in
Mystery Star 4?
Hydrogen____________
(b) What is odd about the spectrum?
Its red shifted because its over to the
right_____