The sun radiates energy at a rate of 3.9 1026 W. (a) Atwhat rate is the sun losing mass? (b) At that rate, howmuch time would it take to exhaust the suns fuel supply?The suns mass is 2.0 1030 kg, and you may assumethat the reaction producing the energy is about0.7% effi cient. Compare your answer with the sunsexpected remaining lifetime, about 5 Gy.
Thursday, December 10, 15 The last lecture 2 iClicker • Everybody gets a point! 3 Constructive Interference (1) § The geometric optics of the previous chapter cannot be used to explain interference § To understand these interference + phenomena we must take into account the wave nature of light § Interference takes place when light waves of the same wavelength are = superimposed § If the light waves are in phase, they interfere constructively, as shown to the right 14 Destructive Interference (1) §If the two light waves are out of phase, as shown to the right, the amplitudes of the waves will sum to + zero everywhere and the two waves will destructively interfere §Here the phase difference between the two waves is π radians, 180°, or = λ/2 16 Thin Film Interference (1) § Another way of producing interference phenomena is partial reflection of light from the front and back layers of thin films § A thin film is an optically clear material with thickness on the order few wavelengths of light § Examples of thin films include the walls of soap bubbles and thin lay