Answer:
So 0 dB does not mean no sound, it means a sound level where the sound pressure is equal to that of the reference level. This is a small pressure, but not zero. It is also possible to have negative sound levels: - 20 dB would mean a sound with pressure 10 times smaller than the reference pressure, i.e. 2 μPa.
Answer:
Length will be 0.491 nm
Explanation:
We have given wavelength of the photon 
Plank's constant 
We know that energy of the photon is given by
We know that energy of photon is also given by
Answer:
t = 1,144 s
Explanation:
The simple pendulum consists of an inextensible string with a mass at the tip, the angular velocity of this is
w = √( L / g)
The angular velocity is related to the frequency and period
w = 2π f
f = 1 / T
w = 2π / T
Let's replace
2π / T = √ (L / g)
T = 2π √ (g / L)
Let's calculate
T = 2π √ (9.81 / 18.5)
T = 4,576 s
The definition of period in the time it takes the ball to come and go to a given point (a revolution) in our case we go from the end to the middle point that is a quarter of the path
t = T / 4
t = 4,576 / 4
t = 1,144 s
