# The wavelength of light emitted from an LED lightbulb that has a frequency of 60 Hz is _____ nm.?

Update:

5 x 1015

5 x 10-14

2.5 x 107

2.5 x 1014

-5 x 1014

These are the choices.

Update 2:

The numbers after 10 are raised.

Relevance
• Given,

Frequency (f) = 60 Hz = 60/sec

Wavelength (λ) = ?

Speed of light (c) = 3 x 10⁸m/sec

We know that:-

Wavelength (λ) = c/f = 3 x 10⁸m/sec / 60/sec

= 0.05 x 10⁸m x 10⁻⁹/10⁻⁹

= 5 x 10¹⁵ x 10⁻⁹m

∴ Wavelength (λ) = 5 x 10¹⁵nm.

• This was correct. Thank you. And thank you for showing the work.

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• This question has an error. The 60Hz is the driving frequency and has nothing to do with the emitted wavelength. The Human visible wavelength of light is between ~380 to 740 nm ,3.8x10^-7 to 7.4x10^-7 m.

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• First of all, an LED lightbulb doesn't have a wavelength, it has a spectrum - usually a narrower blue peak and a wider yellow peak.

Next, since the LED emits visible light, the wavelength is (roughly) between 350 and 700 nm.

An LED lightbulb will only emit very small amounts of em radiation at 60 Hz (it's simply too small to be an effective emitter), and that radiation wouldn't be called light, but ELF.

Whoever asked this question should be repurposed as sandbag at Fukushima.

• Actually, it would be more like SLF unless you are an atmospheric scientist. I like the "sandbag at Fukushima" remark especially - I think I'll steal it.

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• Anonymous
3 months ago

Your question is flawed. Electromagnetic radiation with a frequency of 60 Hz is not visible light but falls instead in the Super Low Frequency band of radio waves. The associated wavelength is 5*10^6 m or 5*10^15 nm, which matches your first choice.

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• somewhere between 380 and 720 - otherwise it would be infrared or ultraviolet.

The frequency/wavelength of the light produced is NOT determined by the frequency of the Alternating Current that feeds the LED

• 5 x 1015

5 x 10-14

2.5 x 107

2.5 x 1014

-5 x 1014

These are the choices.

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• Anonymous
3 months ago

Wavelenght λ (m) = speed of light c (m/sec) / frequency ( 1/sec)

λ = 300*10^6 / 60 = 5*10^5 m = 5*10^14 nm

• 5 x 1015

5 x 10-14

2.5 x 107

2.5 x 1014

-5 x 1014

These are the choices.

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• LED means light emitting diodes. These have specific frequencies of emission. It does not matter which power supply you use. But LED work on DC voltages of 1 to 10 V maximum.

• 5 x 1015

5 x 10-14

2.5 x 107

2.5 x 1014

-5 x 1014

These are the choices.

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• Wavelength = speed of light/frequency

=3×10^5 km/s / 60 cycles per second=5000km.

Are you sure your numbers and units are right?

• 5 x 1015

5 x 10-14

2.5 x 107

2.5 x 1014

-5 x 1014

These are the choices.

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