# Recent content by ussrasu

1. ### Balmer Series & Lyman Series

The formula is 1/lamba = R (1/2^2 - 1/n^2) sorry if that doesnt make sense But i will put in the number 2 in n for one wavelength and infinity for the other wavelength - and then subtract the 2 answers to get the wavelength range? Is this along the right lines?

In the textbook in a previous example - it says that the C-14 activity in a living tree is 255 Bq - that is where i got that value from but i wasnt sure if i could use that value in this question - ie is it always 255 Bq in living trees?!? The half-life is in s^-1 - therefore the answer...
3. ### Minimum amount of energy necessary to remove a proton from 42-Ca atom

Thanks for that
4. ### Balmer Series & Lyman Series

Yeh but what i dont understand is how many different energy levels there are for each of the series? Like does it go on forever or does it stop at a certain number? Ie they start at n = 2 or n = 3, but where do they stop? Do they go up to infinity? Is it as simple as plugging the number in for...
5. ### Balmer Series & Lyman Series

Q: What are the widths of the wavelength intervals over which (a) the Lyman series and (b) the Balmer series extend? (Each width begins at the longest wavelength and ends at the series limit.) (c) What are the widths of the corresponding frequency intervals? Express the frequency intervals in...

Q: A 50-g chunk of charcoal is found in the buried remains of an ancient city destroyed by invaders. The carbon-14 activity of the sample is 200 decays/min. Roughly when was the city destroyed? A: I used R = Ro*e^(-lambda*t) and t1/2 = ln2/lambda t1/2 = 3.834*10^-12 s-1 and 200...
7. ### Minimum amount of energy necessary to remove a proton from 42-Ca atom

Q: What is the minimum amount of energy necessary to remove a proton from the nucleus of a 42-Ca atom, thereby converting it into a 41-K atom? The former has a mass of 41.958618 u, the latter 40.961825 u, and the hydrogen atom has a mass of 1.007825 u. My answer: 42-Ca --> 41-K + 1-H...
8. ### Frequency of EMR

This is what my demonstrator told me to use?
9. ### Frequency of EMR

Can some please review this question and tell me if the working looks correct? Please advise of any mistakes i may have made. Thanks Q: UV radiation (wavelength = 250 nm) falls on a metal target, and electrons are liberated. If the maximum kinetic energy of these electrons is 1.00*10^-19 J...
10. ### Approximate the minimum kinetic energy of an electron

Q: Approximate the minimum kinetic energy of an electron confined to a region the size of an atom (0.10 nm) How would one go about solving this? What equations/principles are involved and how do we use them? Seems like a simple question but i have no idea where to start? :confused...
11. ### Electrical Potential Energy

I dont know how to do it - with the small amount of info given? Can someone show me how to work it out please? Thanks! :smile:
12. ### Gauss' Law and Flux Question

What happens in each of the situations though? i.e in parts a) b) and c) - what is different in each of them? And how do you explain these observations in terms of Gauss' Law and Flux? Thanks :smile:
13. ### Cell Membrane Question

The membrane of a cell is electrically equivalent to a parallel plate capacitor. A typical cell has a spherical shape with a radius 10 μm and it has a potential of −60 mV with respect to outside. The thickness of the membrane is about 0.01 μm, and it has a dielectric constant of 2. Find: (a)...
14. ### Electrical Potential Energy

I have no idea what principles i am supposed to use in this question? Could someone show me how to do this question please? Thanks :smile: Calculate the electrical potential energy of two protons separated by 1 nm, and compare it with their gravitational potential energy. Estimate how heavy...
15. ### Gauss' Law and Flux Question

I dont really understand Gauss' law - any help with this question would be appreciated? Coaxial cables are made of a copper wire in the center and a concentric cylindrical shell of copper outside, with insulating material in between and outside the shell. The charge per unit length of the...