Transcript PPT
Bit of Administration …. • Lab 2 – New observation dates: March 22 - April 5 • No need to duplicate observations in hand! – New due date: April 9 at my office • Homework • Reading – BSNV pp. 153 - 168 • No office hours today – Feel free to e-mail for later in week Astronautics • Interplanetary Travel • The Central Concept … The paths of interplanetary spacecraft are simply orbits around the Sun … And the spacecraft obey the same physical laws as do planets. Astronautics • Transfer Orbit = Minimum Launch Energy • Launch in the direction of motion of the launch platform. • Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit. (Aphelion - point of orbit most distant from Sun Perihelion - point of orbit closest to Sun) Transfer Orbit for the Moon Astronautics • Transfer Orbit = Minimum Launch Energy • Launch in the direction of motion of the launch platform. • Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit. (Aphelion - point of orbit most distant from Sun Perihelion - point of orbit closest to Sun) •Advantages - Fuel efficiency •Disadvantages - Long travel time Astronautics • Gravity Boosts • Gain in energy due to gravitational “slingshot” around a more massive body. • Note: More massive body loses energy, but in case of planet and spacecraft this is not a problem! Astronautics • Gravity Boosts In frame of Jupiter but Jupiter is moving … In frame of Solar System Astronautics • Gravity Boosts - NASA missions The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests passing per second - has units of cycles per second, or Hertz • Speed - for light, c = 3x105 km/sec 3 x 105 km/sec Wavelength The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests per second • Speed - for light, c = 3x105 km/sec Small wavelength Large frequency Large wavelength Small frequency The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests passing per second - has units of cycles per second, or Hertz • Speed - for light, c = 3x105 km/sec n c l The Physics of Light • Electromagnetic Spectrum 1 km = 1000 m 1m 1 mm = 0.001 m = 10-3 m 1 mm = 10-6 m (“micron”) 1 nm = 10-9 m (nanometer) The Physics of Light • Electromagnetic Radiation • Light acts as an electric force - - - - - - - - - - - - - • Light acts as a magnetic force N N N S S S S S N N S S S S N N N N S S S N N N The Physics of Light • Electromagnetic Radiation Antenna The Physics of Light • Doppler Shift The Physics of Light • Doppler Shift • Source moving toward observer or observer moving toward light source Shorter Wavelength Higher Frequency Blueshift • Light source moving away from observer or observer moving away from light source Longer Wavelength Lower Frequency Redshift The Physics of Light • Doppler Shift • Source across observer’s line of sight Same Wavelength as emitted Same Frequency as emitted No Shift The Physics of Light • Doppler Shift l lrest v c v = velocity of light source or observer (+ => toward each other) l = rest wavelength l = change (shift) in wavelength c = 3 x 105 km/sec