15. The H, lines measured on earth from opposite ends of the sun's equator differ in wavelength by 0.091 . If the solar diameter is 1.4 x 10 m, estimate the period of rotation of the solar material, assuming this rotation to be the cause of the effect. Take the wavelength of the alpha line on earth to be 6560 . 16. The wavelength of H, line of hydrogen is 6561 . Calculate the width of the H, line due to Doppler broadening at 6000 K. The maximum speed with which hydrogen atoms approach or recede from the (Ans. 24.7 days) 3 spectrometer is given by kinetic theory of gases by the equation 1 mv = 2 KT. Take K = 1.38 2 x 10 23 m = 1.673 x 10 27 in S.I. units. 17. What is the speed of an observer approaching a star directly if he observes that half the radiation emitted from the star is bunched within a cone subtending an angle of 10 radian? [Hint: cos 0 = 1 02/2 = B] (Ans. 21B = 0.533 ) (Ans. v = 0.9995 c)