EMR propagates as a wave phenomenon and interacts as a particle (wave-particle dual nature of light). No paradox, since light either interacts or propagates, never both at the same time. The particle is the (spin 1 massless uncharged) particle called the photon which carries energy E=hn, momentum p=E/c and angular momentum h/2p. h=6.626196E-34Js.
Extra: Spectroscopists often use an energy unit called the electron volt, the energy gained by an electron falling through a potential difference of one volt, 1eV=1.60217733E-19J.
Basic optics (geometrical optics) takes light to travel in straight lines or "rays"and when a ray strikes a surface or interface the ray obeys:
Basic telescope formulae include:
What magnification in the above telescope gives an exit pupil of 7 mm?
04. How much more light does a 3 metre diameter telescpe collect than a 1 metre diameter telescope?
08. What is meant by the angular resolution of a telescope?
08* What is the angular resolution of a one metre telescope?
09. What limits the angular resolution of the AAT 3.9 metre telescope at Siding Springs?
15. Why did Roemer's observations of the Galilean satellites support the heliocentric, but not the geocentric hypothesis?
16. Would you purchase a telescope advertised as 600X over one advertised as 50/120X?
17. The observing cage at the prime focus of the Palomar 5 metre telescope is about one metre in diameter. What fraction of the light is blocked by the cage?
18. Compare the light gathering power of a 10X50 monocular to that of the dark adapted eye (assume 5mm pupil diameter).
18* Estimate the limiting magnitude of 10X50 binoculars (assume the limiting magnitude of the unaided eye to be +6).
20. What is the magnifying power of a 20 cm f/10 Newtonian telescope with (a) 9 mm and (b) 25 mm eyepieces? What is the exit pupil diameter in both cases?
22. Those Schmidt-Cass telescopes really are getting popular with amateurs. How come? (I want one.)
08. There are actually three definitions. The strictest is completely resolved where the first minimum of the diffraction pattern (Airy disk) of one object falls on the first minimum of the other: angle=2.44*wavelength/aperture. Rayleigh's criterion is half this, so the first minimum of one diffraction pattern lies on the maximum of the other -- two point sources appear to be merged but can be distinguished without too much trouble. Usually we just say the angular resolution is wavelength over aperture (radians) multiplied by 206265 (arcsec in a radian). This is Dawe's criterion. For visible (555 nm) light a one metre aperture yields a resolution of 555E-09*206265/1=0"1145 so a 3.9m telescope like the AAT should be able to resolve 0"1145/3.9=0"03, three hundredths of an arc second.
09. But the AAT rarely resolves a second of arc because of atmospheric "seeing".
15. The 2 AU difference in distance between conjunction and opposition gives a sixteen minute variation in eclipse predictions according to Copernican cosmology. The geocentric theory gives nil (or whatever the epicycle might give).
16. No. Besides, the 50/120X comes with two eyepieces!
17. Goes as aperture squared -- (1/5) squared is 1/25 -- four percent. Not much.
18. Just aperture squared again! (50/5) squared is 100 times -- this amounts to a difference of five magnitudes. Should reach 11th mag with 10X50's.
20. 20 cm f/10 has objective fo=200 cm so (a) fo/fe=200/0.9=222X (e.p.=0.9 mm), (B) fo/fe=200/2.5=80X (e.p.=2.5 mm). Note: M=fo/fe=a/e.p. so e.p.=fe/f-ratio!
22. Because they are incredibly compact and easy to use! But expensive.