[填空题]
A sound wave is traveling in warm air wtcz.bpn ;2sqk)5-su ihen it hits a layer of cold, dense air. I;q -.zptu2)cib5n sski gzev9. c8q8cf the sound wave hits th 8i.qgec9zvc 8e cold air interface at an angle of 25$^{\circ} $, what is the angle of refraction? Assume that the cold air temperature is $ - 10 ^{\circ} C$. and the warm air temperature is $ + 10 ^{\circ} C$. The speed of sound as a function of temperature can be approximated by v=(331+0.60T) m/s where T is in $ -10 ^{\circ} C$. $^{\circ} $
