2.2声音的特性-2019-2020学年八年级上册初二物理【教材解读】（人教版）

!""!st({| +,-.!t}!!3-" ©ª#jW*èÑ[\W,$ o!£¤#Do��Nn¨âã#YZ £�áÜ W,DaV�Ö*��Nó+3 ¬öüâ ã�! !!"9§Å2%J¦)op' Ei¨J^}|Ë%¦À- �}N$.ÖEi%5¼� Ö!�*jW%ST�oQ �Ö*�� !#"K@Ei-�}|*� e%ós.ÖEi%_Ei¿ s�Ö�e)Ò�S%(Õ ¿kðñ:Ei�Ö*��ü!j*W, �!jþ !jV�Ö*��/¨îW,*èÑ#aV�Ö¤�%!�j W*W,£è'�Ö¤�%!�jW*W,£Ñ *p CD#qX '2®~����?SW,*jW*®+*?S%:§N"&1¿� �ÖP0?S*Wh*jW®+§$ tDo#«0 !!"jW^­ýY��*�eDj�*�ÖP0�3%̂ S¦­ýY% rs±5C Ö}¬!.N'_�¥Ä�a N"&hiåæ¬!-�"nà Î¥Ä)}¬!8�a*'_! `4U÷EB4e\àÕ�* j$Æ¢V."¥ÄÔk F� Õ�;2*Bz"ácÃÄ}5 *��lJhi�0�! =tu£¤Do��N n¨âã#YZ �)�minϯ"C)¥+£ ,;-.*1$oÅmp"�è -.�÷xÔk*gg"�k� ��qU÷¥Ä)¹*�#! Ôk�Óá*Õ��rs"! &# Â�Do ÓÔggdÔk" �rggk-.! #tugsæg" �Ó�N&vv! CcCDpþef# Ó*45�èw"TUÓÔ)Ä Ó*)àÓ*$ÓÔ*45V8 RÙ&9kÝ"qxÀ�à)ý �*¼8�Ó! �ý-�àÓ�ÄÓ! P0?S*jW���e�S$ !#"W,*èѶjW*(÷»)%9(XèW)(ZÑW)Y*èÑN¶ W,$¦�á�%ø1!j*W,(¥øè%Xj(ZjW,è$ !*"�ÖP0*èÑñ!jV*+w&i2ü){+3$¦�ðñ:% !jV*�e¦�%P0¦Ñ'�e¦G%P0¦è$ vCq�wCq !!"ø*5#P03²#øÚyõ+¥*jWP0+¦¨*3²$r =øÚy5¥*P03²)fM#)AB¥#))))AB$ !#"Üj®Dsj®#ø\)P0è�#))))AB*j[\Üj®%̀ L¼\Üëøß5#*ËÏ')P0Ñ�#)AB*j[\sj®%̀ L¼\Ñ�øß5#*:Ï$ !*"øü¦ÎÖa*!jü5#P03² !/!"9§Å2%���S*èéûOÈ+?Sèe*d%'4@¡ðû @£��!�(%C!!")(DE!#")("8!*")(FG!6")*Wy%°��(DE!#") W*û@N !!!" !! !!-!!!!!!0!!!!!!1!!!!!!2 01#Þ!Õ��r Ôk*BzO:ò*BC! íôõyiN"Oyi �µAÕ��Ó"Ê�y´�,*cg"yi  �µP¯PÏÕ�"Õ�*�rP¯Pg"¬�ÔkÚ�P¯Pg" K*%C&!'+*DE&#'+*"8&*'+*FG&6'+ç}ÔV8R*yiO2)-)0)1! ¬�8R*DE&#'+Ô*yiO-! 23#- '# +,-2!~$!!1-" ©ª#aboY%jW*�´[\.e$ o!£¤#ßxx)#y� £�áÜ .eDùï`å+3 ¬öüâ ã�! !!"9§Å2%'»³5¤üýæ%ÇÈ^ Ì�¼Ë%fWh¦{*»Ë�¾üýæ !#"'6m7ââ¡ðWh_¼�Ö%5¦ 5Wh!�*jW%��üýæ½¹à* �e !*"'6m7'b¡ðWh%ós5¦5W h!�*jW%��üýæ½¹à*�e . D þô .�'?S*b¡ðWhT%üýæ½¹T*�e?S%5¥ *jW.e?S%üýæ½¹T*�e¦)%Wh�Ö*�e ¦)%jW*.eR¦) ßxx)#y� !!"�� "½¾#aV�ÖT%y�Eá$V*�)��$ #.eD��*34#��¦)%.e¦)'��¦-%.e¦-$ $'®+§Ø2.eD��*34 '2®~��%!]?S.ejW*®+?S%9§Å2$ !#"-..e*Q(`å jW*.e¢3D��+3»%Yñø��!jV*�x+3$� �!jV¦�%jW¦.8%5¥*jW.e¦-'��!jV¦x% 5¥*jW.e¦)$ !()" Fz;{|x)#BC ! ! ! ÿnà�ý| -ÇÓÔ !!!! ýz¨ä§ÓÔ� {"�|eÓ×a !! CPQ�ÆÕj" eÓN- F�*ÕjPÆ"ÓÔ*_$ PÆ! ePFz;CD#&}'c&~' îïE*¼¨g*Ô>}-` ë+ú*¼¨g*Ô>}-A ¯+"À*OÔk¦gú¦g"R *~gÓÔ+*gÓ��+*x�g �+*gÓ®�+"À*OÓÔ* _$! (# n;Ñ'�W#�«BC -)0L"C��uû�"0)1 L"C��hi�0�"2L" C��U÷ð9�"Z�vk ª# -.*,¨"Ô�-.! !/"":�