Understanding Blackbody Radiation General Astronomy Questions
Hydrogen is the most common element in the universe. (Harlan Ellison, a science fiction writer, popularized the expression “The two most common elements in the universe are hydrogen and stupidity.”) Cold hydrogen between the stars tends to give off radio waves at a frequency of 1420 MHz (megahertz, or millions of cycles per second).
What is the wavelength in meters of this radiation?
Wavelength =( )m
A star has a surface temperature of 8950 K.
At what wavelength (in nanometers) will it give off maximum light?
λmax =( )nm
The maximum light emitted by a star is at a wavelength λmax = 305 nm.
What is the temperature T in Kelvin of the star?
T =( )nm
We observe photons of light coming from a bright star in the night sky. One of those photons has a frequency 5.8 × 1014 Hz (or cycles per second).
What is the energy of the photon in joules?
Energy =( )J
Understanding Blackbody Radiation: It turns out that stars behave like an idealized object that scientists call a blackbody. Thus, understanding blackbodies and how they give off energy helps us to understand how stars shine. For a blackbody, the higher its temperature, the smaller the __________ at which it gives off the peak amount of radiation. Thus, really, really hot stars will shine most intensely with _________ radiation. Also, the higher a star’s temperature, the greater the ______ of radiation coming from it. This last statement is called _____________ law.
a. When I broke my leg, the doctor took an image of my broken bones using _____
b. My TV remote control uses ____ to send instructions to the TV set
c. When I go to the neighborhood sports bar (with the big dish on the roof) to watch a game, the broadcast uses _______
d. The laser pointer our astronomy professor is so fond of uses ____________
e. When people with light skin get a sunburn, the radiation responsible is __________
f. When a Russian or Japanese nuclear reactor has an accident or meltdown, the fear is that _________ will be released in the process g. When I want to heat up some left-overs quickly, I use ______________
(Infrared, Gamma-ray, Microwave, Radio, Ultraviolet, Visible, X-ray)
Doppler Effect Helps Astronomers and Highway Police. When Christian Doppler in the middle of the 19 th century discovered that when the source of waves is moving toward us or away from us, the __________ of the wave changes, little did he dream of all the ways his discovery would be used in our time. When an astronomer takes a spectrum of a nearby star moving toward us, he can determine its _______ coming toward us by measuring the _________ of a __________. When a highway patrol officer points a radar gun at a speeding driver, he will measure the equivalent of a __________ as the driver moves away from the officer’s position.
g. Spectral line
The Lessons of the Rainbow. When white light passes through a prism, the colors separate into a rainbow of light, through a process scientists call ______________. When a star’s light is put through a spectroscope, we generally see the rainbow of colors, one blending into the next, known as the ______________ and some dark lines which is the _____________. When astronomers see a hot, not very dense gas glowing, a spectroscope generally shows the _______________. Each element leaves a unique “signature” in the spectrum, by having its own pattern of ___________. If the source of light we observe in a spectroscope is moving toward us or away from us, there is a change in the colors observed due to ____________.
a. Absorption spectrum
b. Continuous spectrum
d. The Doppler effect
e. Inverse square law
f. Emission spectrum
h. Spectral lines
i. Wien’s Law
Have two other questions from the pictures, I’ll send you a pdf