Heavy stone of mass m is hung from the ceiling by a thin 8.25-g wire that is 65.0 cm long. when you gently pluck the upper end of the wire, a pulse travels down the wire and returns 7.84 ms later, having reflected off the lower end. the speed of sound in the room is 344 m/s, and the stone is heavy enough to prevent the lower end of the wire from moving. if the wire is vibrating in its second overtone, what is the wavelength of the sound it will produce?

0.9m

Explanation:

The equation that relates frequency and wavelength of the sound produced is , where c is the speed of sound in the room in this case. First we must know the frequency at which the string is vibrating.

The equation that relates frequency on a string with its longitude L and pulse speed v while vibrating on the armonic n is:

The velocity of the pulse v is the length of the string L divided by the time it takes the pulse to travel the string. The time given t is the time to go forth and back, so the time to travel the string once is half that. We have then:

We must put all together now:

Since the frequency of the sound produced f is the frequency of the vibrating string , and taking into account that the 2nd overtone is the 3rd armonic, we finally have:

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia