The wavelength of the first harmonic of the standing wave is 2L.
<h3>What is a standing wave?</h3>
A standing wave is one in which the obvious points remain fixed as the vibration continues. A standing wave occurs in a wind instrument such as a trumpet, saxophone etc.
We know from the formula of the first harmonic that the wavelength of the first harmonic of the standing wave is 2L.
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The potential difference,electric current ,resistance and new electric current will be 12 V,4 A,3 Ω,2 A.
<h3>What is resistance?</h3>
Resistance is a type of opposition force due to which the flow of current is reduced in the material or wire. Resistance is the enemy of the flow of current.
The energy in terms of the charge and potential difference is;
E= qV
60=5 C × V
V= 12 V
The electric current is found as;

From the ohm's law;
V=IR
12=4 ×R
R=3Ω
If the voltage is constant and the resistance is doubled, then the new electric current is half of the previous condition;

Hence, the potential difference,electric current ,resistance and new electric current will be 12 V,4 A,3 Ω,2 A.
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Tan x = AC / BC
tan (4.3) = 35 / BC
BC = 35 / tan (4.3) = 465.485 m
Speed = 1300 km/h = 361.111 m/s
465.485 / 361.111 m/s = 1.289 seconds
hope this helps