Question

The power of sound from speaker of radio is 10 W, the power of sound from the speaker of radio is 400 W by increasing the volume of radio. The power increased in dB as compared to original power is nearly

• A. 8
• B. 12
• C. 13
• D. 16

Answer 1

Answer: (D)

16

Given, initial power = $10W$ and final power = $400W$

We have to calculate the power increase in dB.

Let us suppose that loudness is denoted by $L$.

Here, $L_f-L_i=10\log \frac{I_f}{I_o}-10\log \frac{I_i}{I_o}$

$\Delta L=10\log \frac{I_f}{I_i}$

We know that $P\propto I$

So, $\Delta L=10\log \frac{P_f}{P_i}$

$\Delta L=10\log \frac{400}{10}\approx 16$

So, D is the correct answer.