The part of the electromagnetic spectrum has a shorter wavelength than ultraviolet light is x-rays.
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:
M au = Fs - M g au = upwards acceleration; Fs = scale reading
Fs = M (au + g) scalar quantities where g is positive downwards and au is positive upwards - Fs is the net force acting on the person
If the acceleration is zero Fs = M g and the scale reads the persons weight
If the elevator is decelerating then au is negative and the scale reading Fs = (g - au) M and the scale reading is less than the weight of the person
B the mass of the solar object determines whether the gravity of the object unless the solar object has Sonic property's such as a neutron star which can be the size of Pluto but have the mass of 900 solar masses
1.) equal volume of different substances have "different" masses.
2.)The more closely packed arrangement the particles of a substance have, "increases" its density.
3.)the SI unit of power is "Watts".
4.)an iron nail sinks in water but floats on " mercury ".
5.)balloons used for advertisements are filled with " helium" gas.
6.)"Conduction" is the primary mode of heat transfer in liquid and gases.
I hope this helps you...