Electromagnetic wave allows us to control television with a remote control.
This electromagnetic wave is invisible.
Infrared is that electromagnetic wave that is used to control television using remote control.
Explanation:
It is given that,
Diameter of loop, d = 1.4 cm
Radius of loop, r = 0.7 cm = 0.007 m
Magnetic field, 
(A) Magnetic field of a current loop is given by :
I is the current in the loop
I = 27.85 A
(B) Magnetic field at a distance r from a wire is given by :
r = 0.00222 m
Hence, this is the required solution.
Answer:
about 14.7°
Explanation:
The formula for the angle of the first minimum is ...
sin(θ) = λ/a
where θ is the angle relative to the door centerline, λ is the wavelength of the sound, and "a" is the width of the door.
The wavelength of the sound is the speed of sound divided by the frequency:
λ = (340 m/s)/(1300 Hz) ≈ 0.261538 m
Then the angle of interest is ...
θ = arcsin(0.261538/1.03) ≈ 14.7°
At an angle of about 14.7°, someone outside the room will hear no sound.
