GATE-2018 (24) :Wyllie – Time average equation

GATE-2009

28. The minimum appreciable amplitude recorded by a seismometer is 0.2mm and the maximum one is 20cm ,then the dynamic range in dB is

A) 80 B) 60 C) 40 D) 20

Solution:

Dynamic range (DR) = 20 log₁₀(A_max/ A_min) dB ----------------------------(1)

Where,

A_max- Maximum amplitude recorded on seismometer =20 cm

A_min- Minimum amplitude recorded on seismometer =0.2 mm = 0.02 cm

DR= 20 log₁₀ (20/ 0.02) dB

= 20 log₁₀ (2000/2) dB

= 20 log₁₀ (1000) dB

= 20 log₁₀ 10³ dB ( log₁₀¹⁰ =1)

= 20* 3

=60

Therefore Dimanic range (DR) = 60 dB