Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as
now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as
now we know that
so now the distance from friend must be 47 cm
Answer:
False
Explanation:
As we know that, the Balmer series gives the n values as,
.
.
Now the value of wavelength can be calculated as,
.
Here, .
And .
Now,
.
Therefore,
Therefore, the wavelength of Balmer series lies in visible region which is 547 nm.