1-The speed of electromagnetic waves in a vacuum is 3E8 m/s. (a) Wvaelengths in

Question

1-The speed of electromagnetic waves in a vacuum is 3E8 m/s. (a) Wvaelengths in the visible part of the spectrum (light) range from about 4E-7 m in the red. What is the range of frequencies of light waves? (b) The range of frequencies for short-wave radio is 1.5 megacycles/s. What is the correspondent wavelength range? (c) X-rays are also electromagnetic. Their wavelength range extends from about 5E-9 m to 1.0E-11 m. What is the frequency range of X-rays?

2- Graph y=sin ? and y=cos? and find the sum by the principle of superposition.

3- Graph y=2sin? and y=sin(?+?) and add them by the principle of superposition.

4- Find graphically the sum of y=1/2 sin? and y=2cos?.

Explanation / Answer

Wavelength (L) = Speed of Light (c) divided by the Frequency (f) ; L = c / f
c = 299,792,458 m/s or *roughly* 3E8 m/s
http://en.wikipedia.org/wiki/Speed_of_li...

(a)
4E-7 m = (3E8 m/s) / f
f = 3E8 m/s / 4E-7 m
f = 7.5E14 Hz = 750E12 Hz = 750 TeraHertz

7E-7 m = (3E8 m/s) / f
f = 3E8 m/s / 7E-7 m
f = 4.25E14 Hz = 425E12 Hz = 425 TeraHertz

(a) Answer: Visible Light is from 750 TeraHertz to 425 TeraHertz

(b)
1.5 MegaCycles per second = 1.5 MegaHertz = 1.5 MHz = 1.5E6 Hz
L = 3E8 m/s / 1.5E6 Hz
L = 200 meters

300 MegaCycles per second = 300 MegaHertz = 300 MHz = 300E6 Hz
L = 3E8 m/s / 300E6 Hz
L = 1 meter

(b) Answer: Shortwave Radio is from 200 meters to 1 meter

(c)
5E-9 m = (3E8 m/s) / f
f = (3E8 m/s) / 5E-9 m
f = 6E16 Hz = 60E15 Hz = 60 PetaHertz

1E-11 m = (3E8 m/s) / f
f = (3E8 m/s) / 1E-11 m
f = 3E19 Hz = 30E18 Hz = 30 ExaHertz

(c) Answer X-Rays is from 60 PetaHertz to 30 ExaHertz

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