Quanta questions! (1 Viewer)

[Dumbarse]

1)explain why the hydrogen spectrum contains many lines when a hydrogen atom only contains one electron?

2) The ground state potential of the hyrogen atom is -13.6 eV. A photon of energy 14.6 eV collides with an elecron in the ground state of a hydrogen atom. What will be the energy of the ejected electron?

3) a transmission electron microscope accelerates electrons through a potential difference of 5.00 x 10^3 V
(i) calculate the velocity of each electron after it has been accelerated.
(ii) Calculate the maximum possible resolution of the microscope from the wavelength of the electrons.

?? help appreciated

 

[BlackJack]

Will continue to crash Q2Q tomorrow, but I can answer q1...

1) The electron on the H-atom can have different excited states. When the atom gets heated, the electron will jump to different shells depending on how much energy it absorbs.
When the e- cools, it can follow different paths back down to its base energy at 1st shell. eg 7th shell-> 2nd shell-> 1st shell. Clearly there are multiple ways, and with Planck's eq. E=hf 9and c=fl) each jump will release a photon of different wavelength. Thus there are many spectral lines.

 

[Dumbarse]

thanx

but its more the other 2 i need help with
ive never done examples like these before...
spice girl i need your help!

 

[McLake]

2) The ground state potential of the hyrogen atom is -13.6 eV. A photon of energy 14.6 eV collides with an elecron in the ground state of a hydrogen atom. What will be the energy of the ejected electron?

Forgive me if this is dumb, but:

14.6 - 13.6 = 1 eV ???

3) a transmission electron microscope accelerates electrons through a potential difference of 5.00 x 10^3 V
(i) calculate the velocity of each electron after it has been accelerated.
(ii) Calculate the maximum possible resolution of the microscope from the wavelength of the electrons.

3)i)
V = Ed
V = (F/q)d
are you missing a value here????

3)ii) ...

 

[Dumbarse]

haha, yeh McLake!, 1eV was right!
your as lost as i am for the microscope one


alright how bout this one
An electron of energy 1.80 x 10^-18 J collides inelastically with an electron of a hydrogen atom in its ground state n1 = (-2.18 x 10^1. What will be the energy of the electron after the collision??

how do u do it??

 

[McLake]

Originally posted by Dumbarse

An electron of energy 1.80 x 10^-18 J collides inelastically with an electron of a hydrogen atom in its ground state n1 = (-2.18 x 10^1. What will be the energy of the electron after the collision??

Inelastic ???
Hmmm .... I'll get back to you

 

[SgtSlick]

Originally posted by Dumbarse
3) a transmission electron microscope accelerates electrons through a potential difference of 5.00 x 10^3 V
(i) calculate the velocity of each electron after it has been accelerated.
(ii) Calculate the maximum possible resolution of the microscope from the wavelength of the electrons.
?? help appreciated [/B]

Dont worry about this type of question buddy, it simply wont be examined, the syllabus for Ideas 2 Implementation does not specify that students need to be able to calculate the resolving ower of a microscope, merely describe qualitatively why the resolving power is greater for an electron microscope than a regualer light microscope (i.e. smaller wavelength, ability to differentiate bewteen smaller spaces...) So yeah they just wont ask that man...For i2i and q2q its more important u know the significance of particular theories as well as what they are, and also stuff about the workings of cro and tv's. Also dont forget to do mass defect calculations, im sure they will rear their butt-ugky heads. GL.

-SgtSlick

 

[Bambul]

I remember doing Quanta to Quarks this time last year and I couldn't understand a thing there.

I guess I forget stuff much faster than I learn it.

 

[SgtSlick]

BTW - I meant quanta to quarks, and i was just considering q3, are u sure thats all the info given to u?

As McLake said, it would be easiest to say v=Ed, and transposing this gives v=(F/q)d where q is the charge on an electron. Yet the Force cannot be determined, whilst v=W/q, and by substitutuin 5x10^e for v, we get 5x10^3=W/q which is still unsolvable. SO im sorry but I think u have missing info...

 

[spice girl]

Originally posted by Dumbarse

3) a transmission electron microscope accelerates electrons through a potential difference of 5.00 x 10^3 V
(i) calculate the velocity of each electron after it has been accelerated.
(ii) Calculate the maximum possible resolution of the microscope from the wavelength of the electrons.

Dumbarse, forget the other question bout inelastic electron collision. It's WAAY outside syllabus

Anyway
W = qV
= 1.6 *10^-19 * 5.00 * 10^3 = 8 * 10^-16

This work energy is pure kinetic energy.
1/2 mv^2 = 8 * 10^-16
mass of electron = 9.019 * 10^-31
v^2 = 1.77 * 10^15
v = 4.21 * 10^7 (phew...it's less than c)

ii) lambda = h / mv
= 6.626 * 10^-34 / ((9.019 * 10^-31) * (4.21 * 10^7 ))
= 1.75 * 10^-11
= 0.0175 nm

By Rayleigh's criterion (see http://230nsc1.phy-astr.gsu.edu/hbase/phyopt/raylei.html or the Jackaranda pg something...), max resolution is of the same order as wavelength.
i.e. ~0.01nm (this is res under ideal conditions)

 

[McLake]

Re: Re: Quanta questions!

Originally posted by spice girl

W = qV
E = 1/2(mv^2)

Knew there was a formula somewhere ...

 

[Dumbarse]

ohhh, so the wavelength is the resolution??
thanx!

do we have to know
energy for nth energy level
E = -13.6/n^2 ???

yehh i thought it was a bit much, it was in my stoopid physics in context fat arse textbook. it either doesnt explain a section, or goes way over detail

 

[Viator]

Think of it like this, if the wavelength is bigger than the object, you won't be able to see it right? Simply because the light can't fit in there.
So the smallest possible thing you could see is the size of the wavelength, hence the resolving power.
The resolving power in reality isnt the same as the wavelength though, a little bit less..

 

[Dumbarse]

yehha, but do we still calculate it using

lamda = h/mv ??

and no one answered my first question
do we have to know all the quarks and leptons, their charges, and symbols>>??

 

[Viator]

Yeah, that's how I would do it.

 

[spice girl]

Originally posted by Dumbarse
do we have to know all the quarks and leptons, their charges, and symbols>>??

Umm,...i doubt it. Just learn that there are six quarks, six leptons, the properties of quarks and leptons, what mesons and baryons are, and what protons and neutrons are made of.

You might wanna learn a bit about force particles (photon, intermediate-vector bosons W+, W-, Z (i think), gluons, and the "gravitron")

That's about it...

And no, you don't NEED to know E = -13.6/n^2. Just learn Balmer's equation, and you can do anything (required in syllabus).

And yes, lamda = h/mv is the only way to convert between velocity and wavelength of particles

 

[Dumbarse]

thanx spiceygal
what u reckon you'll get in this physics test>>

 

[spice girl]

around 96 if feeling good on the day...
a bit less if not...

I did crap at trials, not really sure how much more i've studied so far...
I'm good at calculations, just not good at giving them the society BS...and when calc's constitute 15%, it's not very good...

PS: don't quote me for what you "should" study, i've no liability for the BOS pulling some weird-ass question out of their asses...just to make that clear

 

[Dumbarse]

i like your accuracy

its gunna be hard to get that sorta mark but, u must know your work pretty damn well

 

[Minai]

he's the smartest person on this forum, i think he can manage

yeah, I was doing all the questions in that red Success One Physics book, and in Q2Q i encountered a question:

Name the quarks making up:
1. a proton, and
2. a neutron

i mean, i didnt really fully cover the fact that protons consist of two Up's and 1 down etc
however is that still within the scope of the syllabus?
ive noticed spice's comment on it

(note: the standard model section is the only section of the physics course i hate with a passion)