Recent content by djerry

Homework Statement An optical telescope with a 12mm eyepiece makes the Moon appear to have an angular diameter of 30 degrees. What is the focal length of the telescope's objective? Homework Equations magnification=focal length of objective/focal length of eyepiece The Attempt at a...

Well it should be negative. But when you calculate you get a positive as you're taking a smaller number (the observed) from the true wavelength. Do I just assign a negative because it's getting smaller?

I calculated the change in wavelength as 0.2111m-0.2095m=0.0016m.

The wavelength observed was smaller, which implies the object is moving toward the observer.

Homework Statement Atomic hydrogen emits a characteristic spectral line with a frequency of 1421 MHz. A radio telescope observes this line in a certain galaxy at a frequency of 1432 MHz. Is the galaxy approaching or receding, and at what speed (in km/s)? Homework Equations The Attempt at...