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Quiz On Horsehead
Nebula
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[Physics
of Horsehead Nebula]
Give all answers to
3s.f. unless otherwise asked.
c
= 3.0*108 m/sec e = -1.69*10-19
c 1 A.U. = 1.5 *108 km
1. The temperature
of interstellar space is typically -263oC. Express this in kelvin
to the nearest degree.
kelvin
2. The visible
region ofthe electromagnetic spectrum is from
l = 420nm (violet) to l
= 700nm (red).
(a)
Calculate the frequency of a photon of wavelength 700nm.
x1014
Hz
(b) The
energy of this photon giving the answer in joules.
x10-19
J
3. It is
more usual to work in electron volts.
(a)
Convert your anwser from 2(b) to eV.
eV
(b) An electron
in a hydrogen atom makes a transition from the n=4 level to n=3, an energy
difference of 0.66eV. Calculate the wavelength (to nearest nm) of the photon
produced.
nm
4. A star
may be considered a good approximation to a black body radiator. Wien's
Law applies: ( lmax
T=0.0029).
(a)
Use Wien's Law to estimate the wavelength at which the sun emits most of
its radiation, if the surface temperature is 5800K.
nm
(b) Use
the same law to calculate the corresponding wavelength for a massive O
type star with surface temperature of T = 30000K.
nm
5. If the
HH nebula is 1600 light years away,
How
many A.U.s is this ?
*108A.U.
6. As viewed
from the earth the Horsehead Nebula subtends an angle of 0.02 degrees.
(a)
Convert this to radians.
*10-4rad
(b) Calculate
the distance across the Nebula in light years.
light
years
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