Physics, 10.10.2019 01:30 biaxialpower789

Aparticular metal has a work function of 1.05 ev. a light is shined onto this metal with a corresponding wavelength of 324 nm. what is the maximum velocity of the photoelectrons produced? (hint: 1ev = 1.6022 x 10-19 j, mass of an electron = 9.11 x 10-31 kg)

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Answer from: rivermadds1514

Velocity of electron will be $v=0.986\times 10^6m/sec$

Explanation:

We have given work function of metal $\Phi =1.05eV=1.05\times 1.6\times 10^{-19}J=1.68\times 10^{-19}J$

Wavelength of the light $\lambda =324nm=324\times 10^{-9}m$

So energy is given by $E=\frac{hc}{\lambda }$ , here h is plank's constant and c is speed of light

So $E=\frac{6.6\times 10^{-34}\times3\times 10^8}{324\times 10^{-9} }=6.11\times 10^{-19}j$

For a metal we know that $E=\Phi +KE_{MAX}$

So $KE_{MAX}=E-\Phi =6.11\times 10^{-19}-1.68\times 10^{-19}=4.43\times 10^{-19}$

Now kinetic energy is given by $KE=\frac{1}{2}mv^2$

$4.43\times 10^{-19}=\frac{1}{2}\times 9.11\times 10^{-31}v^2$

$v=0.986\times 10^6m/sec$

So velocity of electron will be $v=0.986\times 10^6m/sec$

Answer from: Quest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

Answer from: Quest

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

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