Pathways to Astronomy

Stephen E. Schneider

Chapter 26 Detecting Light - all with Video Answers

Educators

Chapter Questions

Problem 1

Suppose that you are using an older $C C D$ camera that collects only $40 \%$ of the light that would otherwise be gathered. How would this affect the magnification of the image you are taking? How would this affect the brightness of the image?

Mayukh Banik

Numerade Educator

03:15

Problem 2

If a visible-wavelength photon striking a CCD can liberate one electron, approximately how many electrons could be liberated by an X-ray photon with a wavelength of 1 nm? with a wavelength of $0.1 \mathrm{nm}$ ? How might it be possible to distinguish between one photon of higher energy versus many photons of lower energy?

Katie Mcalpine

Numerade Educator

03:39

Problem 3

One of the 10 -m diameter Keck telescopes can observe 500 -nm visible-wavelength photons. If a radio telescope observing $10-\mathrm{cm}$ photons was built to be proportionally as large relative to the photons it was observing, what would its diameter be? What about a gamma-ray telescope observing 0.01 -nm photons?

Joseph Fritchman

Numerade Educator

03:39

Problem 4

The diameter of your eyés pupil is about $8 \mathrm{mm}$, while the Arecibo radio telescope has a diameter of about $300 \mathrm{m}$ For what wavelengths of light does the Arecibo radio telescope have the same relative size to the wavelength as your eye does to visible light?

Joseph Fritchman

Numerade Educator

01:40

Problem 5

To provide clear images, the surface of a telescope mirror should be smooth to within $1 / 10$ of a wavelength of the light being collected. What size is this for a visible-wavelength telescope? for a radio telescope? for a gamma-ray telescope? Compare the sizes of these largest imperfections to physical objects.

Aja S

Numerade Educator

02:36

Problem 6

Small knots of gas in the Crab Nebula are observed to be moving away from the position of the dead star at its center. Measurements of the position from photographs taken in 1940 and 1990 show that knots originally located 150 arc seconds from the center had moved 8 to 9 arc seconds farther out. From this information, estimate the range of dates when the explosion might have occurred.

Kratika Bhadauria

Numerade Educator