Answer:
We use X-rays to help the injured, Radiowaves to communicate or entertain, and Visible light to see.
Since,
Speed = Frequency * WaveLength
=> WaveLength = Speed / Frequency --- (A)
Frequency = 13.0 kHz.
As the radio waves are electromagnetic waves, their speed is equals to the speed of light. Therefore,
Speed = C =

Plug in the values in equation(A):
A => WaveLength =
Ans: Wavelength = 23.077 kilometers.-i
Answer:
f = 692 N
Explanation:
given data:
f =800N
a =1.2 m s^{2}
m= 90 kg
from newton's second law
net force 
therefore we have from above equation
ma =F - f
putting all value to get force of friction
1.2*90 = 800 - f
f = 692 N
Answer:0.1759 v
Explanation:
Intensity of wave at receiver end is
I=
I=
I=
Amplitude of electric field at receiver end

Amplitude of induced emf
=
=
=
Answer:2800000j
Explanation:
For us to know the kinetic energy of the vehicle,
Where m is the mass
And v is the velocity
Then, K.E=1/2mv^2
While, K.E=1/2×3500×40^2
Therefore, our answer will now be
K.E=2800000j