unit overview part 1 p1 34
TRANSCRIPT
October 31, 2013
Exploring The Night Sky
A compilation of the class notes that were presented.
October 31, 2013
Night Sky Observations1. Group/No and Name 2. Date, time, and location3. Weather conditions: Is it windy? Is it cloudy, hazy, etc? How much of the sky does it cover? Where are the haze or clouds?4. Light pollution & sky brightness: Is the sky uniformly dark? How bright compared with bright celestial objects (ex: Moon, planets or stars)? Which parts of the sky are brightest? What are the sources of light that are making the sky bright?5. What did you observe? Describe in as much detail as you can your observation of astronomical objects. Which objects do you think you saw? Which constellations? Was the moon visible? If so, what did it look like?6. Length of observation: How long did you observe the night sky? Did you walk around to find the best view? Did your parents help you?
October 31, 2013
Working with a LensLenses in telescopes help us to observe objects in the night sky with more clarity.
The main function of a lens is to collect as much light as possible. Although they magnify to some degree, the most important thing they do is collect light. More on that later...
Work with your desk partner to complete this lab before the end of the class. If not completed by end of class, this lab MUST be completed during study hall.
October 31, 2013
Working with a Lens
Front View Side View
1. Make a simple sketch that shows both a front view and a side view of the lens. Use shading to show dimensionality.
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2. Describe the shape of the lens.
• The lens is perfectly round in shape. In thickness, it is thickest in the middle, gradually becoming thinner towards the edges.
• The shape of this lens is called a double convex. This means that it curves outward on both sides of the lens. If it curved out on only one side, it would be called a single convex lens.
• Convex lenses are the type of lenses that are used in telescopes.
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3. Hold the lens above a section of print. While looking through the lens, slowly pull it away from the paper.
a) Describe the observation (use details and support with a sketch if necessary).
The print becomes more and more magnified. At a certain point, just past the half-way distance between the paper and eye, things become blurry and smaller.
October 31, 2013
3b) How far (in centimeters) from the paper is the lens before the print becomes unfocused? How did you determine when the print became 'unfocused'? Did you agree with your partner?
The focal length of the lens is 17.5 cm. How close were you?
Focal length is the distance between a lens and the point where the light rays come together in focus.
October 31, 2013
4. Hold the lens close to but not touching your eye and look through it across the room. Describe what is observed while looking through the lens.
The images appear blurry and somewhat larger/magnified.
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5. Again, hold the lens up to your eye and look through it (across the room, not down at the paper). Slowly move the lens until it is an arm's length away from your eye and describe what you observe.
At arm's length, the image is clear but flipped upside down.
October 31, 2013
6. Move the lens and this sheet of paper so that they are directly underneath one of the overhead lights. Focus the light so that it passes through the lens onto the rectangle below. Watch the image on the paper while slowly moving the lens closer, then farther away from the paper. Describe what is observed and draw a simple sketch of the observation.
There is an exact image of the light fixture focused on the paper! It looks like what a photograph of the light would look like.
October 31, 2013
7. With your back to the window, hold the lens up so that it is out in front of you. Hold the lens about 17 cm in front of the index card, focus the light onto the paper, and describe what you see.
The image on the paper is an upside down image of the scene behind you. By moving the lens slightly forward or slightly backward, different parts of the scene come into focus. Anything that is reflecting enough light can be picked up and projected by the lens.
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What is the main function of a telescope?
October 31, 2013
Quick Review ...
What is the main function of a telescope?
What is the only reason we are able to see things?
What is the name of the type of lens used in a telescope?
October 31, 2013
• While I am checking cards, add the following:
> Concave Mirror: A curved, opaque surface that reflects light so that it can be focused and magnified.
October 31, 2013
Flashcard Definitions• Telescope: A device used to gather EMR and magnify objects in
the sky.
• Electromagnetic Radiation (a.k.a. EMR): All the kinds of energy released into space by stars like our sun. The only difference between different types of EMR is the length of their waves.
• Visible Light: The range of EMR that can be seen by the human eye (a.k.a. 'white light'). Can be broken down into the colors of the rainbow (red, orange, yellow, green, blue, violet)
Think of EMR as "sunshine"
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• Wavelength: The distance from the crest (top) of one wave to the crest of the next.
• Spectrum: A range of something from one end to the other.
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• Electromagnetic Spectrum (EMS): The range of wavelengths of EMR from longest to shortest: radio waves, microwaves, infrared radiation, visible light, ultraviolet light, x-rays, gamma rays (see following slide).
R - M - I - V - U - X - G
Rabbits Might Invade Vanderbilt University's X-ray Garden Here's a mnemonic for you!
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Source: http://librarian.net/science/electromagnetic_spectrum.jpg
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• Refraction: The 'bending' of light (it's really a change in direction).
• Reflection: The 'bouncing' of light (also a change in direction).
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• Convex: A shape that has a surface that curves outward.
• Concave: A shape that has a surface that curves inward ('caves' in).
• Convex Lens: A curved lens that refracts light so that it can be focused and magnified.
• Concave Mirror: A curved mirror that reflects light so that it can be focused and magnified.
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• Optical Telescope: A telescope that collects visible light and produces images that can be seen by the human eye.
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• Refracting Telescope: A device that uses a transparent, convex lens to collect and focus visible light.
• Reflecting Telescope: A device that uses an opaque, concave mirror to collect and focus visible light.
Both the refracting and reflecting telescope are optical telescopes because they colled visible light.
October 31, 2013
Radio Telescope: A device that collects and focuses the largest waves of EMR.
Space Based Telescope: Devices located in space so they can collect the entire range of EMR.
Observatory: A location designed and equipped for making celestial observations.
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OK, we know the definition of refraction, but what IS it exactly, and WHY does it happen?
Today you're going to start some hands on exploration to see what's going on. Next week we'll dive into the 'why' part of it.
Work with your desk partner and get through at least the first refraction lab, 'The Broken Pen'.
Refraction
October 31, 2013
Quick Review ...What is the main function of a telescope?
What is the only reason we are able to see things?
What is the name of the type of lens used in a telescope?
What is refraction?
What is the difference between the following terms?
Translucent, Opaque, Transparent
October 31, 2013
Refraction Revisited • Today you're going to finish exploring the effects of
refraction on what we see.• Work with your desk partner to complete the
remaining refraction activities.• Remember, you are being graded on details. • If you finish all of the activities, begin practicing
your key term flash cards.
October 31, 2013
Quiz Reminders:
1. A(n) -?- telescope collects only visible light to focus and produce images.
acts like a 'fill-in-the-blank' space.Could be 'a' or could be 'an'. Simply means, you don't know if the following word starts with a vowel or a consonant.
Format:
2. Not all words are used. NO words are used more than one time!Strategy:
1. ALWAYS guess!
2. Lightly mark off words in the word pool as they are used but don't mark them out so you can't see them - might need them later!
October 31, 2013
Quick Review ...
What is the main function of a telescope?
What is the only reason we are able to see things?
What is the name of the type of lens used in telescopes?
What is refraction?
What is the difference between the following terms?
- opaque, translucent, transparent
October 31, 2013
Refraction
• Refraction is the 'bending' of light - really it's a change in the direction in which the light is traveling.
October 31, 2013
Refraction Labs Debrief
Get out a red grading pen and your 'Refraction' labs.
Make sure you name and group/no. are clearly written!
Take notes on this stuff! Use the space on the back of your lab.
October 31, 2013
RefractionIn the vacuum of space, light travels at a constant speed of nearly 300,000,000 m/s.
In car-driving terms, that's about 671 million miles per hour!
October 31, 2013
Refraction
> Outer Space 299,792,458 m/s> Atmosphere (air) 298,925,574 m/s > Water 225,056,264 m/s> Glass 197,231,880 m/s
Mnemonic to aid in remembering the exact speed of light: (count the letters in each word)
'We Guarantee Certainty, Clearly Referring To This Light Mnemonic'
When light travels through matter, it slows down:
2 9 9 7 9 2 4 5 8
October 31, 2013
Refraction• When light passes from one substance to another, such as
air to water, it changes speed. When it changes speed, the light rays bend, or, change direction.
• Have you ever noticed how different things look in a swimming pool when you're standing up and looking down towards your feet and legs that are in the water?
• What's going on?
October 31, 2013
'The Broken Pen'What observations did you make about the pen when you viewed it in the beaker full of water?
pen in exact center
pen to left of center
pen on farleft of center