Exam 4: A Universe of Universal Laws

Stars A and B have identical luminosities,but star A is nine times brighter than star B.If star A is 9 parsecs from Earth,how far away is star B?

Stars A is four times more luminous than star B,and it is also four times farther away than star B.How does the brightness of these two stars compare?

An astronomer obtains two samples of rarefied gas.She heats the first gas and finds that it produces a spectra with a series of bright lines.She places the other gas in front of a hot blackbody and finds a continuous spectrum with a series of dark lines.If the wavelengths of the dark lines are the same as those of the bright lines,she infers that the samples have identical:

An astronomer takes a spectrum of a nearby star.She finds that its absorption lines all appear at shorter wavelengths than expected from laboratory measurements.She should conclude that the star is:

The radiation spectrum produced by a blackbody depends on its:

An astronomer takes spectra of two stars,A and B.She discovers that the continuous part of star A's spectrum peaks at 200 nm,while the continuous part of star B's spectrum peaks at 800 nm.Both stars have dark bands superposed on this continuous spectrum,and the locations of these dark bands are the same in both stars.What do you know about the composition of the stars? Why?

A reading light contains a dimmer switch that can vary its luminosity from 10 W to 100 W.If the device produces just the right amount of light when set to 10 W and held at a distance of 10 centimeters,to what value should you set the wattage if you hold it 20 centimeters away?

Light is:

Which portions of the electromagnetic spectrum must be observed from space?

An astronomer measures the spectra of two stars,A and B.She finds that star A is nine times more luminous than star B and is three times as hot.How are their surface areas related?