Astronomy 115 HW 3 Part 2 Name:____________________________________

Due March 23rd ID# (last4) :________________________

Show all your calculations where applicable.

1) Which type of electromagnetic radiation has the highest frequency and the shortest wavelength?

2) What is the range of wavelengths that a human eye can see?

3) What is the range of frequencies that a human eye can see?

4) How does the light-gathering power of the largest telescope in the world compare with that of the human eye? (The largest is the 10 m Keck. See by the numbers 5-1 pg 76)

5) How is the binding energy of an electron related to the size of its orbit?

6) Describe two ways an electron can become excited.

7) Which process produces what kind of spectra: Continuous, Emission, Absorption. Fill in the blank.

a) light bulb _________________

b) molten iron __________________

c) star _______________________

d) Neon light _______________________

e) florescent light ______________________

f) the sun ____________________________

8. Human body temperature is about 98.6 degrees F (= 310 K). Use Wien's Law to find the wavelength that humans radiate the most energy. What kind of radiation do we emit?

9. Fill in the blanks.

When we discuss the temperature of a star, we mean the temperature of its ___________________.

Stellar spectra are _________________ spectra. The surface of a star, called the ______________________, produces a

_____________________ spectra and the lower density gases in the stellar atmosphere absorb certain wavelengths of light,

producing an _____________________ spectra that we observe. The most common spectral lines studied

in stars are the __________________ lines of Hydrogen. The strength of the Balmer lines depends on the

__________________ of the stars surface. In cool stars like the sun, most atoms have their electrons in the

_______________ state. As a result, we find______________ Balmer lines in cool stars. Hot and cool

stars have ______________Balmer lines and medium-temperature stars have __________________ Balmer Lines.

10. Observations of a star show it to have a black body spectrum that peaks at a wavelength of 3000 nm. Answer the following. Show your calculations.

a) What type of electromagnetic radiation is a wavelength of 3000 nm?

b) What is the temperature of the star's surface? (Use Wien's Law)

c) What Spectral Class is this Star?

d) How much energy per sec does the star radiate from each square meter of its surface? (Use Stefan-Boltzmann Law)

11) Determine the temperatures and spectral classes of the following stars based on their spectra. Use figures 6-15 and 6-16.

a) medium-strength Balmer lines, strong helium lines.

b) medium -strength Blamer lines, weak ionized-calcium lines

c) strong TiO bands

d) very weak Balmer lines, strong ionized-calcium lines

12) In a laboratory, the Blamer beta line has a wavelength of 486.1 nm. If the line appears in a star's spectrum at 486.3 nm, what is the star's radial velocity? It is approaching or receding? Red shifted or Blue shifted?