The speaker at the concert has the sound intensity level of 100 dB if we listen from the distance 5 m. How far from the speaker does the intensity level drop to the safe value of 85 dB?

5.42 meters

Explanation:

Sound intensity varies inversely with the square of distance:

I = k / r²

When r = 5, I = 100.

100 = k / 5²

k = 2500

I = 2500 / r²

When I = 85:

85 = 2500 / r²

r = 5.42

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000

where is the circuit diagram ?