1. Frequency from Wavelength 12 points
Compute the frequency of red light with wavelength 650 nm and blue light with wavelength 450 nm using c = lambda nu. Use c = 3.00 x 10^8 m/s. Which photon has higher frequency?
Instructions
Show reasoning, units, diagrams or plots where useful, and source acknowledgments. Numerical answers without explanation receive limited credit. Eligible submissions may be revised after feedback.
Concrete Problems
2. Doppler Shift of H-alpha 16 points
The H-alpha line has rest wavelength 656.3 nm. In a galaxy spectrum it is observed at 658.0 nm. Estimate radial velocity using v/c approximately equals Delta lambda / lambda. Is the galaxy moving toward or away from us along the line of sight?
3. Collecting Area 12 points
Compare a 20 cm telescope with a 2.0 m telescope. How many times larger is the collecting area of the 2.0 m telescope? What does this improve, and what does it not automatically fix?
4. Resolution Limit 14 points
Using theta = 1.22 lambda/D, compare diffraction-limited angular resolution for D = 0.10 m and D = 1.0 m at lambda = 500 nm. Give the ratio and explain why real ground-based images may not reach this limit.
Recommended OpenStax Practice
- OpenStax Astronomy 2e, Astronomical Instruments exercises, Review Question 1, extracted index line 8320: components of a modern astronomical instrument.
- OpenStax Astronomy 2e, Astronomical Instruments exercises, Review Question 4, extracted index line 8326: why larger telescope apertures are better.
- OpenStax Astronomy 2e, Astronomical Instruments exercises, Figuring for Yourself 28, extracted index line 8390: pupil diameter and light gathering.
- OpenStax Astronomy 2e, Astronomical Instruments exercises, Figuring for Yourself 30, extracted index line 8394: Keck telescope light gathering compared with an amateur telescope.