Physics: Post your doubts here!

Hassan Ali Abid

Hassan Ali Abid

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1357911 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_41.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_ms_41.pdf
Q-8 cii

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_4.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_ms_4.pdf
Q-9 b.. and Q-11 biii

Can anyone help me with these.:unsure::unsure:
Click to expand...
DSC_0409.jpg
 
Hassan Ali Abid

Hassan Ali Abid

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midha.ch said:
your 3rd question is similar to 1st question. Here instead of the ratio, you are asked to find the time taken to reach that ratio
If you have understood my answer to first question it's easy to find the result for third question. But if you still have confuson then let me know.

I'll skip numerical calculations for your 4th question
Consider Initial activity is A1
after time t, Activity reduces to (A1 x 1/10)
put the values in the equation of activity
you have already found decay constant in previous parts
now just put the values and solve it.

If you are still unsure or confused about any of the answers, then let me know :) I'll be glad to help:)
Click to expand...

I have understood All the parts except one......let me try them again ...if i'll feel any difficulties i'll ask u IA .:)
and thanks :)
 
meerul264

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6(a)
Take note that how stationary waves are formed is often asked in exams.
So it's important to know how to write (just knowing how it is formed but not knowing how to write the answer will not give you credit).

How to answer:
So here is what I usually write when this question appears (after nth times):
"When two waves of the same frequency travels in the direction opposite to each other overlaps, the resultant displacements of the wave is
the sum of the displacement of individual waves. Producing nodes and anti-nodes. (The speed of the stationary wave is the speed of one of the overlaping waves."

6(b)
Although this kind of question is not frequently asked (from the past papers I've done so far), it's important for you to memorize the experiments to demonstrates stationary waves
(including how to draw the diagram).

According to the syllabus I've read, this include:
1. Demonstration using mechanical waves (stretched strings)
2. Demonstration using microwaves
3. Demonstration using air column

How to answer:
*The objective is to find the wavelength of sound in air using stationary wave.

sw_microwave.png

"The source of sound is the microwave transmitter producing incident wave.
The receiver is the detector connected to a c.r.o to detect nodes and anti-nodes of the stationary wave.
The hard surface is made to reflect the incident microwave.

The incident microwave from the transmitter are made to be reflected off the hard surface. When the incident wave and reflected wave overlaps, nodes and anti-nodes are produced.
When the receiver is moved from the hard surface to the microwave transmitter, the detector will show alternating high and low readings, indicating the locations of anti-nodes and nodes respectively.
The wavelength of the stationary wave is 2 x (distance between adjacent nodes or anti-nodes)."

*If anyone can improve my answer or have a better answer for this question please let me know :)*

6(c)(i)

intensityx.png

At the nodes, amplitude is minimum ( zero).
Since amplitude is proportional to intensity, the intensity is also zero ( I = k A^2).
At anti-nodes, amplitude is maximum.
Since amplitude is proportional to intensity, intensity is also at maximum. (I = k A^2)

6(c)(ii)

Use the formula v = f l where l is wavelength.

v = 340 m/s
l = 2 x (distance between adjacent nodes or anti-nodes)
 
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Thought blocker

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