Practise the method.Example 1A logarithmic magnitude scale is M=log10(I0I). One event has magnitude 3, another 8. How many times as intense is the second?Show worked answerAnswer: 100000Subtracting magnitudes gives log10(I1I2)=5. Thus I1I2=105=100000.Example 2Sound level is L=10log10(I0I) dB. Intensity increases by factor 100000. By how many decibels does L increase?Show worked answerAnswer: 50Change in L=10log10(100000)=10×5=50 dB.Example 3pH=−log10(H), where H is the hydrogen-ion concentration in Lmol. If H=10−7, find pH.Show worked answerAnswer: 7log10(10−7)=−7; taking its negative gives pH=7.