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firstly,

A blue supergiant star has surface temperature 29kK and has total power output 100000 times that of the Sun.

where is the wein peak of this stars balckbody curve?

I got lambda=9.99*10^-8m, which i know is right.

now, radius of sun is 6.96*10

^{8}m, find radius of supergiant..

so ratio here should give the supergiant a surface area of A=100000A of sun.. solving for that gives r = 2.11*10^11m... but it tells me its wrong???

secondly,

A photoelectric experiment uses 265 nm light and a silver target.

Find max kinetic energy of photoelectrons.

Kmax=hf-W

_{0}

h=6.626*10

^{-34}

f=c/lambda=1.13*10^15

W

_{0}for silver = 7.43*10^-19

subbing in gives Kmax = 5.738*10^-21J.... and it also tells me that is wrong???

thirdly,

Suppose you want to observe neutron diffraction in a crystal with 0.28 nm spacing between lattice planes.

Find the momentum of neutrons having wavelength equal to this spacing.

found p=2.4*10^-24 kg*m/s

Find the kinetic energy of neutrons having wavelength equal to this spacing.

found K=1.7*10^.21 J

If these neutrons constituted an ideal gas, what would be the gas temperature?

How the heck do i do that :S??

thanksss so much for any help!