Physics, 20.07.2019 20:00 mercedezosborne

An electron has a kinetic energy of 3.00 ev. find its wavelength. (b) what if? a photon has energy 3.00 ev. find its wavelength.

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Answer from: bentonknalige

The wavelength of the electron from the given kinetic energy is $7.1 \times 10^{-10} \ m$ .

The wavelength of the electron from the given photon energy is $4.13 \times 10^{-7} \ m$ .

Momentum of the electron

The momentum of the electron is calculated as follows;

$P = \sqrt{2Km} \\\\P = \sqrt{2 \times (3 \times 1.6 \times 10^{-19} \times 9.11 \times 10^{-31} } = 9.35 \times 10^{-25} \ kgm/s$

Wave of the electron

The wavelength of the electron is determined by using De Broglie's equation.

$\lambda = \frac{h}{p} \\\\\lambda = \frac{6.6 \times 10^{-34} }{9.35 \times 10^{-25}} = 7.1 \times 10^{-10} \ m$

Wavelength of the electron from the given photon energy

E = hf

$E = \frac{hc}{\lambda} \\\\\lambda = \frac{hc}{E} \\\\\lambda = \frac{6.6 \times 10^{-34} \times 3\times 10^8}{3\times 1.6 \times 10^{-19}} \\\\\lambda = 4.13 \times 10^{-7} \ m$

Learn more about wavelength of photons here: link

Answer from: StephenCurry34

(a) The electron kinetic energy is
K=3.00 eV

which can be converted into Joule by keeping in mind that
$1 eV=1.6 \cdot 10^{-19}eV$
So that we find
$K=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The kinetic energy of the electron is related to its momentum p by:
$K= \frac{p^2}{2m}$
where m is the electron mass. Re-arranging the equation, we find
$p= \sqrt{ 2Km}= \sqrt{ 2 ( 4.8 \cdot 10^{-19} J)(9.1 \cdot 10^{-31} kg) } =9.35 \cdot 10^{-25} kgm/s$

And now we can use De Broglie's relationship to find its wavelength:
$\lambda= \frac{h}{p}= \frac{6.6 \cdot 10^{-34} Js}{9.35 \cdot 10^{-25} kg m/s} =7.06 \cdot 10^{-10}m$
where h is the Planck constant.

(b) By using the same procedure of part (a), we can convert the photon energy into Joules:
$E=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The energy of a photon is related to its frequency f by:
E=hf

where h is the Planck constant. Re-arranging the equation, we find
$f= \frac{E}{h}= \frac{4.8 \cdot 10^{-19} J}{6.6 \cdot 10^{-34}Js} =7.27 \cdot 10^{14}Hz$

And now we can use the relationship between frequency f, speed of light c and wavelength $\lambda$ of a photon, to find its wavelength:
$\lambda= \frac{c}{f}= \frac{3 \cdot 10^8 m/s}{7.27 \cdot 10^{14} Hz} =4.13 \cdot 10^{-7} m$

Answer from: Quest

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.

Answer from: Quest

answer: i'm not sure which is which for i get confused on it all the time but i can tell you that the answer lies with the convex and concave devices. i hope this you. have a good day and best of luck to you!

explanation:

For which optical devices does d sometimes have a positive value?

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An electron has a kinetic energy of 3.00 ev. find its wavelength. (b) what if? a photon has energy...