A few things for Physics MCQ to remember (points that people usually forget or don't know at all)

[Diva#1]

Could u please tell me the frequencies of all the waves in elcetromagnetic spectrum ?
Doggybros

 

[XPFMember]

Could u please tell me the frequencies of all the waves in elcetromagnetic spectrum ?
Doggybros

AsSalamoAlaikum Wr Wb!

This might help you: http://xtremepapers.com/community/threads/electromagnetic-spectrum.16126/#post-273053

 

[Doggybros]

Could u please tell me the frequencies of all the waves in elcetromagnetic spectrum ?
Doggybros

Every wave in electromagnetic spectrum has speed of 3×10^8 metres per second.
Use the formula speed = wavelength × frequency to find the frequency.
This is a lot more simpler than remembering frequencies. Remembering wavelengths is quite easy, but frequencies are hard and I prefer to find them this way.
If you want, you can find out frequencies for every wave and remember them for your convenience (I wouldn't exactly call it convenience, its cumbersome) in the exams.

 

[johnsth]

Could u please tell me the frequencies of all the waves in elcetromagnetic spectrum ?
Doggybros

da frequencies r:
radio-10^6
micro-10^10
infrared-10^12
visible-10^14
ultraviolet-10^16
x ray-10^18
gamma-10^22.........its not dat difficult...but u can learn it in day way dat other guy said i.e by knowing wavelength.
da wavelengths r:
radio-10^2
micro- 10 ^-4
infrared- 10^-4
visible- 10^-6
ultraviolet- 10^-8
x ray- 10^-10
gamma- 10^-12...hope its easy 4 u 2 remember

 

[thunderingthunder]

da frequencies r:
radio-10^6
micro-10^10
infrared-10^12
visible-10^14
ultraviolet-10^16
x ray-10^18
gamma-10^22.........its not dat difficult...but u can learn it in day way dat other guy said i.e by knowing wavelength.
da wavelengths r:
radio-10^2
micro- 10 ^-4
infrared- 10^-4
visible- 10^-6
ultraviolet- 10^-8
x ray- 10^-10
gamma- 10^-12...hope its easy 4 u 2 remember

thank you very much..2 life savers on the same thread is great thing,you know...you can easily secure 5 to 10 marks

 

[Mad-Eye]

A question similar to this has been asked many times:
When same voltage is applied to each of the following nuclei, which reaches the highest velocity?

For this question, find the ratio of charge to mass. It is directly proportional to velocity and you can equate it to velocity for your convenience in the exams.
__________________________________________________________________________________________________________________________
Explain with example question please someone......

 

[leosco1995]

It might just be me but I think memorizing all of the frequencies (and wavelengths too) is kind of useless. I just learnt the wavelength of visible light (10^-7) and then add/subtract 10^2 on either side of the electromagnetic spectrum, so the wavelength of whatever is just before would be 10^-5, then 10^-3, and so on and the opposite would go for the other side. To figure out the frequencies, just divide the wavelength by the speed of light. Never encountered a problem with any of the MCQs involving this stuff. But still, this could be risky.

 

[Doggybros]

A question similar to this has been asked many times:
When same voltage is applied to each of the following nuclei, which reaches the highest velocity?

For this question, find the ratio of charge to mass. It is directly proportional to velocity and you can equate it to velocity for your convenience in the exams.
__________________________________________________________________________________________________________________________
Explain with example question please someone......

Question is: When same voltage is applied to each of teh follosing......?
1. 14X6 2. 13Y6 3. 18Y7 3. 12Y9
Find the charge to mass ratio, ie. proton to nucleon ratio(notice i said nucleon and not neutron) Then one with highest is the one which has highets velcity.

 

[Diva#1]

Doggybros
johnsth
well i know memorising all the frequencies is hard but i came across some questions where they ask the magnitude of frequency of waves....could u pls please help me in o/n 9 variant 12 ques 22 ?
n thnxx alot for the frequencies..all the best for physics

 

[Diva#1]

thnx alot XPF member

 

[Doggybros]

Doggybros
johnsth
well i know memorising all the frequencies is hard but i came across some questions where they ask the magnitude of frequency of waves....could u pls please help me in o/n 9 variant 12 ques 22 ?
n thnxx alot for the frequencies..all the best for physics

If you know the wavelengths, then I don't think it would take you more than 15 secs to divide speed of light by the wavelength.
As for the question you've asked:
It says longest wavelength. Note that there is a huge difference between UV and visible.
Longest wavelength would be greater than the mean wavelength which I've given.
So instead of 30nm use 100 nm.
Divide speed of light by that and you'll get the answer.

 

[Diva#1]

ohh alryt ...thnxx alot
could i ask u a few more questions if u don't mind ?

 

[Doggybros]

ohh alryt ...thnxx alot
could i ask u a few more questions if u don't mind ?

go ahead try to ask many at once ill be heading to my exam centre soon

 

[Diva#1]

o/n 11 variant 12 Q 26
Q 14 y do we divide the force by two ?? coz its been supported by two tyres ?
Q 15

 

[Diva#1]

O/n 11 vrnt 1
Q 5
6 y cnt it b A ?
15
16
26
28
34

 

[Doggybros]

o/n 11 variant 12 Q 26
Q 14 y do we divide the force by two ?? coz its been supported by two tyres ?
Q 15

q26: the path difference at the given point is half of a wavelength(count them) Use unitary method and you'll get the answer
14 is a question of moments. 30kn acting at the centre and opposing force is acting on the black part. So 30×10 = x × 20 and you'll get the answer 15.
15 use the concept work done = change in energy and you'll get it.

 

[Diva#1]

Thanku very much for ur help ....

 

[Doggybros]

O/n 11 vrnt 1
Q 5
6 y cnt it b A ?
15
16
26
28
34

Im going now this is the last thing im answering.


5 Uncertainty percentage is added when dividing/multplying and uncertainties themselves are added in adding/subtracting If you found the uncertainty percentages you wouldnt get the highest uncertainty to be d but its squared so the uncertainty percentage is doubled and makes it highest.
6 it is a
15 Again, its about moments. Calculate 1 × 7 + 1 × x = 5×2 Keep in mind that the answer is number of points away from the pivot, not the point iself.
16 Initial kinetic energy = ek
For momentum to be conserved, product of mass and velocity must be equal. So final mass is 2m but final velocity = v/2.
Kinetic energy = 1/2 × 2m × (v/2)^2. Subtract it from the initial ek and you get the answer.
26 Read the question carefully. It says amount of compression and not the overall change.
So the more the amount of compression, the less will be its length (common logic)
28 The waves must overlap, doubling single amplitude when there are two sources. But when only once source is there, amplitude halves.
Since intensity/amplitude^2 must always be constant, intensity must decrease by 4 times.
34 Solve by using SI base units. Remember:
Power × Time = Energy
Power = Voltage × Current
Current = Charges/Time
Voltage = Current × Resistance

 

[Diva#1]

okayy
thnx
best of luck !

 

[johnsth]

thank you very much..2 life savers on the same thread is great thing,you know...you can easily secure 5 to 10 marks

welcome....but i not da lyfsaver type guy...cuz m not da geek type guy