Asound is recorded at 19 decibels. what is the intensity of the sound?
1 x 10^-8.7 w/m^2
1 x 10^-10.1 w/m^2
1 x 10^-11.9 w/m^2
1 x 10^-9.4 w/m^2

is the intensity of the sound.

Option B

Explanation:

The range of sound intensity that people can recognize is so large (including 13 magnitude levels). The intensity of the weakest audible noise is called the hearing threshold. (intensity about ). Because it is difficult to imagine numbers in such a large range, it is advisable to use a scale from 0 to 100.

This is the goal of the decibel scale (dB).  Because logarithm has the property of recording a large number and returning a small number, the dB scale is based on a logarithmic scale. The scale is defined so that the hearing threshold has intensity level of sound as 0.

Where,

I = Intensity of the sound produced

= Standard Intensity of sound of 60 decibels =

So for 19 decibels, determine I as follows,

When log goes to other side, express in 10 to the power of that side value,

d. learned preferences i believe is your answer

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.