2 Quick PHYSICS Questions -- Help

Discussion in 'BlackHat Lounge' started by maxxwilliams, Mar 31, 2012.

1. maxxwilliamsJunior Member

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1.) I have a refracting telescope with an objective lens focal length f=200 mm. I have three possible eyepieces I can use with this telescope, having focal lengths of 9 mm, 25mm and 50 mm. I want to look at the planet Jupiter though the telescope, and I would like to make out details on the banded clouds encircling the planet (i.e., I'd like to see a highly magnified view). Which eyepiece would I best use for this?

A. 9 mm
B. 25 mm
C. 50 mm
D. It doesn't matter which one

2.) Similar to the above question, I have a refracting telescope with an objective lens focal length f=200 mm. I have three possible eyepieces I can use with this telescope, having focal lengths of 9 mm, 25mm and 50 mm. I want to look at a cluster of stars which are well spread apart from each other on the sky. Which eyepiece would I best use for this?

A. 9 mm
B. 25 mm
C. 50 mm
D. It doesn't matter which one

If you know how to work these problems then help a fellow black hatter.

2. FreezerburnRegistered Member

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I'm still waiting for the Physics questions ..

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3. maxxwilliamsJunior Member

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Haha it is a Light & Color Physics class. We are on chapter about telescopes and I ma havin a little trouble on these questions.

4. maxxwilliamsJunior Member

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Anybody know any of them?

5. buttulglyJunior Member

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Do your homework you lazy brat.

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6. meatroBANNEDBANNED

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B & C
Total shot in the dark.
Love this kinda stuff.

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1. B
2. C

8. zebrahatElite Member

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Answer is E, technically, none of the above. To see Jupiter and beyond in detail you need a 2X Barlow telescope or better, with a lens giving you 72X magnification. The OP's lens choices lack sufficient power on their own. If you are stuck with the choices, go with the 50mm eyepiece and tweak the system to get the needed magnification.

9. maxxwilliamsJunior Member

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I like your name, buttugly. Probably the way you look also.

FYI... This is not my homework. It is practice for myself, but I wasn't understanding it very well. So I wanted more viewpoints on the answers to these questions.

I have more than 2-question-homeworks assigned to me, because unlike you, I am not still stuck in pre school. Your comment wasn't needed and it showed that you irrelevancy exceeded the time you spent commenting and trying to sound smart.

To those who answered, I thank you

10. Nigel FarageBANNEDBANNED

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I think Buttugly's comments were meant to be a joke.

Last edited: Apr 1, 2012
11. tony23Regular Member

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easy, a + c

12. buttulglyJunior Member

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That it was.

But since he reacted poorly to my dark humor, I shall repeat my statement. Get off your butt and do your homework. This is a marketing forum, not a homework help board.

This is not practice you have idly made up. Anyone that is practicing does not make up tutorial questions without knowing the answer (if you are practicing you typically follow the examples in the book and check the answer immediately to see if you are right). And if you did know the answer, you would not be seeking help here. This is homework.

This is a simple high school physics question about compound lenses. Specifically it is about magnification (M = - F(1)/F(2)). A quick Google search would show you the correct explanation is much shorter time then it would have taken you to open this thread. Which means you already have the explanation, but have yet to understand it. And you won't understand it by repeating the same question here.

BTW - I have 2 degrees from two of Australia's best universities. Have fun catching up.

13. Nigel FarageBANNEDBANNED

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Just goes to show, you never know who you are talking to online. Or in life, for that matter. I didn't believe the whole "I'm just interested in hearing other people's opinions" line of BS, as if scientific answers can be arrived at by democratic process and consensus.

Can't you see this one on "The View", or some equally vacuous TV show, populated by nitwits?

"Does F=Gm1m2/d2 ? Let's ask our TV viewing audience what they think."

Q: "You sir, do you think F=Gm1m2/d2 ?"
A: "Uh, yeah I do, cause I feel dat all the letters of the alphabet should be EQUAL, jus' like colors of da rainbow. Gnome Sayin' ?"
Q: "And you ma'am, what do you think? Does F=Gm1m2/d2?"
A: "I don't feel that it does, because they is all dem letters over there, and only one "F" on that side, and that "F" is up in there, all by itself ain't "all dat".

Einstein is NOT the FATHER!

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Last edited: Apr 3, 2012
14. BlackhatBigfootRegular Member

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I like physics. I was never any good but I'll take a shot at it again.

When Jupiter is closest to Earth(who knows when that is) it is 628,743,036 million km away, or 628,743,036,000,000 km. That is Per Wiki.

Assuming that distance is measured from center to center(likely), the outside surface of Jupiter's main ring is 129,130 km from the center of the planet. I referenced another scientific site for this.

So the distance from the center of the earth to the outer surface of the main ring is 628,613,906 million km

Now subtract from this number the radius(equatorial) of the earth which is 6,378 km. This gets you to the earth's surface(if you are not on Mt. Everest in which case you would be inside the mountain).

So the distance from the surface of the earth to the outer face of the main ring of Jupiter is

628,607,528 million km

The distance the image will appear to be under magnification can be derived from the "lens equation" which is

1/f = 1/object distance + 1/image distance

or

1/200mm = 1/628,607,528 mkm + 1/image distance

or

2.0 x 10^-10 km =1.59047487× 10^-15 km + 1/image distance

or

2.0 x 10^-10 km - .0000159047487 × 10^-10 km= 1/image distance

or

1.9999841 × 10^-10 km
= 1/image distance

1/1.9999841 x 10^10 = 1/image distance

1/19,999,841,000 = 1/image distance

image distance = 19,999,841,000 km

I've edited this number to correct the mistake of not converting mm to millionths of a km so I could subtract like terms( e.g. millionths of a kilometer from a kilometer)

This is how far the main ring seems to be from earth using 200 mm lens or at least my best calculation.

From this point (if I'm right) it should be easy to figure the viewing distances of the additional lenses

This is a little more than 600X. I have binoculars that are 450X. I think you need more power.

Edit*** This is way more than 600x. sorry.

Last edited: Apr 3, 2012
15. tony23Regular Member

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Australia has universities?

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16. BlackhatBigfootRegular Member

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My answer above was way wrong.

The correct answer is 5000 km with the 200 mm lens.

I could show but I'm tired.

Can't resist math stuff.

17. maxxwilliamsJunior Member

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Again, why do you think I have a 2 question homework assignment? This is for myself to better understand the correct answer. The book actually doesn't provide the answer, so I decided to ask on this forum. If you have all those degrees you just mentioned, then why are you here? Go and annoy other students with your fucking degrees... You are obviously not making enough money with your two degrees, so I bet you are hanging around in this forum looking for ways to make money.

Paid the loans yet??

Yes, I DO make tutorial questions without knowing the answer! You can figure out how that answer is correct without knowing it was correct, and work the problem backwards.

Dark humor or not, you are not funny. I hope you didn't graduate with a degree in theater arts, cause you are not very likeable my friend.

Go and dust off the tarantulas from your basement.

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