chemistry?

Question

An AM station broadcasts rock music at 923 on your radio dial." Units for AM frequencies are given in kilohertz (kHz). Find the wavelength of these radio waves in meters (m), nanometers (nm), and angstroms

Answer 1

Frequency = c/l

c = 3 * 10^8 m/s

Frequency = 932000/sec

Meters:

l = (3*10^8m/sec)/(923000/sec) = 325 m

Nanometers:

l = (3.25 *10^2m) * (10^9nm/m) = 3.25 *10^11 nm

Angstroms

l = (3.25 *10^2m) (10^10 Aº/m) = 3.25 * 10^12 Aº

Answer 2

I don't know why all the boring stuff about units and errors and so on ends up in the chemistry classroom. However, here goes:

To find the wavelength in metres, use

frequency x wavelength = speed

In this case, 923 x 10^3 s-1 x wavelength (m) = 2.998 x 10^8 m s-1

And then use 1 m = 10^9 nm = 10^10 A

Answer 3

"An AM station broadcasts rock music at 923 on your radio dial." -- *no* *it* *doesn't*!

All frequencies allocated on the MW and LW bands are multiples of 9kHz (and therefore the digits add up to 9). E.g., Radio Four = 198kHz LW. Talk Sport = 1035 and 1089kHz MW, WABC = 1152kHz MW. The nearest "real" frequencies would be 927kHz or 918kHz.

Get at a hi-fi with a digital tuner, select manual as opposed to preset, and see how the numbers going up and down by 9 for each press of the keys.

Now, your physics teacher probably prefers listening in FM stereo or even DAB, and so didn't know this when he was setting your homework. In which case, you will have to use the formula that speed in m/sec = wavelength in m * frequency in Hz.