5. Show how it is possible by comparing the spectrum of the sun with that of a star to tell whether the star is approaching or receding from the earth.

Review Outline: Light

Light; speed, source, medium.

Straight Line Motion; shadow, umbra, penumbra, eclipse, image.

Photometry; Law of intensity, candle power, foot-candle.

Mirrors; Law of reflection; image—real, virtual; plane, curved, parabolic, mirrors.

Refraction; cause and effects; plate, prism, lens; total reflection.

Lenses; six forms, principal focus, center, lens equation, 1/F = 1/Do + 1/Di.

Optical instruments; eye, defects and correction, camera, microscope, etc.