Anyone a Master of Physics?

Anyone a Master of Physics?

Posers and Puzzles

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H

San Diego

Joined
23 May 07
Moves
2124
03 Oct 07

Again, looking this up:
resonant frequency[f] = 1 / (2 * pi * sqrt (LC))
original f = 1 / (2 * pi * sqrt (LC))
new f = 1 / (2 * pi * sqrt (2L * 2C))
= 1 / (2 * pi * 2 sqrt (LC))
= 1 / (4 * pi * sqrt (LC))
new f / original f = 1/4 / (1/2) = 1/2
new f = 1/2 * original f
So when you double the capacitance and double the inductance, the resonant frequency gets cut in half.

R
The Rams

Joined
04 Sep 06
Moves
13491
03 Oct 07
1 edit

Originally posted by HolyT
Again, looking this up:
resonant frequency[f] = 1 / (2 * pi * sqrt (LC))
original f = 1 / (2 * pi * sqrt (LC))
new f = 1 / (2 * pi * sqrt (2L * 2C))
= 1 / (2 * pi * 2 sqrt (LC))
= 1 / (4 * pi * sqrt (LC))
new f / original f = 1/4 / (1/2) = 1/2
new f = 1/2 * original f
So when you double the capacitance and double the inductance, the resonant frequency gets cut in half.
Yes. What is your source, might I ask?>

R
The Rams

Joined
04 Sep 06
Moves
13491
03 Oct 07

Reflection and Refraction

22. In dispersive materials, the angle of refraction for a light ray depends on the wavelength of the light. Does the angle of reflection from the surface of the material depend on the wavelength? Explain.

H

San Diego

Joined
23 May 07
Moves
2124
03 Oct 07

In reflection, the light remains in the same medium, so its speed remains the same. In refraction, the speed changes. The change in speed is dependent on the wavelength of the light. The frequency remains the same. f[1] = f[2] = v[1]/wavelength[1] = v[2]/wavelength[2].

In its "desire" to find the quickest path from one point to another, the change in speed between the two mediums gives it a path that is not straight (it travels a greater distance in the faster medium and a shorter distance in the slower medium). The amount of change in the path (refraction) is dependent on the speed change which is dependent on the wavelength. In reflection, there's no change in speed, so the wavelength does not matter to how the light finds the quickest path.

R
The Rams

Joined
04 Sep 06
Moves
13491
03 Oct 07

Originally posted by HolyT
In reflection, the light remains in the same medium, so its speed remains the same. In refraction, the speed changes. The change in speed is dependent on the wavelength of the light. The frequency remains the same. f[1] = f[2] = v[1]/wavelength[1] = v[2]/wavelength[2].

In its "desire" to find the quickest path from one point to another, the change in sp ...[text shortened]... change in speed, so the wavelength does not matter to how the light finds the quickest path.
Yep, doing good.

R
The Rams

Joined
04 Sep 06
Moves
13491
03 Oct 07

Mirrors

23. A concave mirror has a focal length of 15 cm. (A) If an object is placed 25 cm in front of the mirror, determine the signs of the focal length, the object distance, and the image distance. (B) Repear part (A) if the object is placed 5 cm in front of the mirror.

H

San Diego

Joined
23 May 07
Moves
2124
03 Oct 07
1 edit

Originally posted by Ramned
Yes. What is your source, might I ask?>
I think this was it: http://www.physics.isu.edu/~hackmart/spl2rci.pdf. I meant that I looked up the formula, but not the entire approach and solution to the problem.

m

Joined
07 Sep 05
Moves
35068
04 Oct 07
1 edit

Originally posted by Ramned
Mirrors

[b]23. A concave mirror has a focal length of 15 cm. (A) If an object is placed 25 cm in front of the mirror, determine the signs of the focal length, the object distance, and the image distance. (B) Repeat part (A) if the object is placed 5 cm in front of the mirror.
[/b]
Not quite sure what you mean by "the signs of the focal length and the object distance". But for the image distance:

The image distance (d_i), object distance (d_o) and focal length (f) are related by:

1/f = 1/d_i + 1/d_o

So (A) f = 15cm, d_o = 25cm => d_i = 37.5cm

(B) f = 15cm, d_o = 5cm => d_i = -7.5cm
(i.e. the image is a virtual image, appearing to be 7.5cm behind the mirror)

R
The Rams

Joined
04 Sep 06
Moves
13491
04 Oct 07

Originally posted by mtthw
Not quite sure what you mean by "the signs of the focal length and the object distance". But for the image distance:

The image distance (d_i), object distance (d_o) and focal length (f) are related by:

1/f = 1/d_i + 1/d_o

So (A) f = 15cm, d_o = 25cm => d_i = 37.5cm

(B) f = 15cm, ...[text shortened]... d_i[/i] = -7.5cm
(i.e. the image is a virtual image, appearing to be 7.5cm behind the mirror)
What I mean is - Positive or Negative for focal length and object distance...

P
Bananarama

False berry

Joined
14 Feb 04
Moves
28719
05 Oct 07

Originally posted by Ramned
What I mean is - Positive or Negative for focal length and object distance...
I think mtthw included that information in his solution. On to the next problem!

u
The So Fist

Voice of Reason

Joined
28 Mar 06
Moves
9908
05 Oct 07

Originally posted by PBE6
I think mtthw included that information in his solution. On to the next problem!
How do I determine the height of a dead tree at my cottage? I need to make sure it won't land on the roof when it falls over.

P
Bananarama

False berry

Joined
14 Feb 04
Moves
28719
05 Oct 07

Originally posted by uzless
How do I determine the height of a dead tree at my cottage? I need to make sure it won't land on the roof when it falls over.
Chop it down from the other side! 😵

u
The So Fist

Voice of Reason

Joined
28 Mar 06
Moves
9908
05 Oct 07

Originally posted by PBE6
Chop it down from the other side! 😵
Then it'll land in the lake and hit the dock and the boat. The other side is a forest so it will just sit up against a tree.

I know it has something to do with measuring the angle from a set distance from the base of the tree but I forget whether it's SIN COS or TAN

Quiz Master

RHP Arms

Joined
09 Jun 07
Moves
48793
05 Oct 07

Originally posted by uzless
Then it'll land in the lake and hit the dock and the boat. The other side is a forest so it will just sit up against a tree.

I know it has something to do with measuring the angle from a set distance from the base of the tree but I forget whether it's SIN COS or TAN
Measure the shadow.

At the same time measure the shadow of a metre high stick.

Then just scale up.

Your answer in metres is tree height = tree shadow divided by stick shadow.

u
The So Fist

Voice of Reason

Joined
28 Mar 06
Moves
9908
05 Oct 07

Originally posted by wolfgang59
Measure the shadow.

At the same time measure the shadow of a metre high stick.

Then just scale up.

Your answer in metres is tree height = tree shadow divided by stick shadow.
That's an excellent Idea except the sun is always shining into the forest instead of behind it.

PB6 told me the Tan equation but I like your Ratio idea. So much simpler.

Thanks