Low pressure sodium lamps, like the ones used in parking lots, emit yellow light. If the wavelength is 5.89 × 10 −7m, what is the frequency? How much energy is in one photon of yellow light?

frequency = 5.09 × 10^14 Hz

Energy = 3.373 × 10^-19 J

Explanation:

1. The wavelength of a substance is calculated using the formula:

λ = v/f

Where;

λ = wavelength (m)

v = speed of light (m/s)

f = frequency of light (Hz)

According to the information given, λ = 5.89 × 10 −7m, v = 3 × 10^8m/s, f =?

Using λ = v/f

f = v/λ

f = 3 × 10^8 ÷ 5.89 × 10 −7m

f = 0.509 × 10^(8+7)

f = 0.509 × 10^15

f = 5.09 × 10^14 Hz

2. Energy of a photon, E, can be calculated thus:

E = hf

Where;

h = Planck's constant (6.626 × 10^-34 J/s)

f = frequency (Hz)

E = 6.626 × 10^-34 × 5.09 × 10^14

E = 33.726 × 10^(-34+14)

E = 33.726 × 10^(-20)

E = 3.373 × 10^-19 J

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