
Cindy asks…
Hertz, Angstrom and nanometers Help?
What is the frequency ( In Mega Hertz) of a beam of red light whose wavelength is 6000 A (Angstrom)? ( 600 Nanometers).

Alain answers:
500 MHz in a theoretical setting,
Closer to 499.654096667 megahertz
Using: Wavelength = Speed of the wave / Frequency
Where the speed of the wave is the speed of light: 299,792,458 meters per second
Frequency is my variable in MHz
and my wavelength is 600nm (for light angstroms are not commonly used)

John asks…
How to relate temperature and doppler effect in spectroscopy?
Sodium atoms, thermally excited, are found to emit light of characteristic wavelength 6000 angstroms. The radiation from a sodium vapor lamp is found not to be perfectly monochromatic, but contains a distribution of wavelengths in the range (6000 +/- 0.02) angstroms. This broadening is caused by the Doppler Effect. Determine the approximate temperature of the sodium source. (Take the speed of light to be 3E8 m/s).

Alain answers:
This is a nonrelativistic problem. The wavelength variation is a factor of 0.02/6000 = 3.333E-6, implying a velocity variation of 3.333E-6c or 1000 m/s. Assuming this is the RMS velocity, for a molar mass M of 0.023 kg it corresponds to a temperature T = M*(vRMS)^2/(3R) = 922.087 K.
I’m not saying the RMS velocity has to be the one implied by “in the range” but it’s the highest of the three velocities (RMS, mean, most-probable) that are easily calculated from the velocity distribution curve, which extends to quasi-infinite velocity. See the ref.

Jemima asks…
Hertz, Angstrom and Nanometers Help?
What is the frequency ( In Mega Hertz) of a beam of red light whose wavelength is 6000 A (Angstrom)? ( 600 Nanometers).
Thanks

Alain answers:
Frequency = Wave Speed/Wavelength
Wave Speed is the speed of light = 3.0 x 10^8 m/s (approximately)
Wavelength is given as 600 nanometers. The speed of light is m/s so the nanometers should be converted by multiplying by 10^-9 as shown:
(3.0 x 10^8)/(600 x 10^-9)
= (3 x 10^8 x 10^9)/600
= (3 x 10^17)/600
= 5 x 10^14 Hertz

Elizabeth asks…
How do you find the frequency of light?
When litium is heated lithum atoms emit photon of red light with a wave length of 6708 Angstroms (10^-10m) What is the frequency of this light.

Alain answers:
Frequency (cycles per second) = c / ?
? Is in meters.

Mark asks…
What is the frequency in mega hertz of a beam of red light whose wave length is 6000 Angstroms?
a 50,000 mhz
b 500,000 mhz
c 5,000,000 mhz
d 50,000,000 mhz
e 500,000,000 mhz

Alain answers:
Use velocity = frequency x wavelength, and assuming red light travels at 300,000,000 metres per second, (and knowing that 1 Angstrom =0.1 nm or 1 x 10^-10 m) the calculation is:
frequency = velocity / wavelength = 3 x 10^8 / 6000 x 10″-10 = 500,000,000,000,000 Hz
So the answer is (e) 500,000,000 MHz
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