Sodium and mercury are currently used in lighting applications. The peak emissions are at 589 nm (yellow) and 436 nm (blue), respectively. What are the corresponding energy and frequency values in eV and Hertz, respectively

Respuesta :

Answer :  The energy and frequency of yellow and blue peak is, 2.10 eV, [tex]5.09\times 10^{14}Hz[/tex]  and 2.84 eV, [tex]6.88\times 10^{14}Hz[/tex]  respectively.

Explanation :

Part 1:

Given:

Wavelength of yellow peak = [tex]589nm=589\times 10^{-9}m[/tex]

Conversion used : [tex]1nm=10^{-9}m[/tex]

First we have to calculate the frequency of yellow peak.

Formula used :

[tex]\nu=\frac{c}{\lambda}[/tex]

where,

[tex]\nu[/tex] = frequency of yellow peak

[tex]\lambda[/tex] = wavelength of yellow peak

c = speed of light = [tex]3\times 10^8m/s[/tex]

Now put all the given values in the above formula, we get:

[tex]\nu=\frac{3\times 10^8m/s}{589\times 10^{-9}m}[/tex]

[tex]\nu=5.09\times 10^{14}s^{-1}=5.09\times 10^{14}Hz[/tex] [tex](1Hz=1s^{-1})[/tex]

The frequency of yellow peak is, [tex]5.09\times 10^{14}Hz[/tex]

Now we have to calculate the energy of yellow peak.

Formula used :

[tex]E=h\times \nu[/tex]

where,

[tex]\nu[/tex] = frequency of yellow peak

h = Planck's constant = [tex]6.626\times 10^{-34}Js[/tex]

Now put all the given values in the above formula, we get:

[tex]E=(6.626\times 10^{-34}Js)\times (5.09\times 10^{14}s^{-1})[/tex]

[tex]E=3.37\times 10^{-19}J[/tex]

Also,  

[tex]1J=6.24\times 10^{18}eV[/tex]

So,  

[tex]Energy=(3.37\times 10^{-19})\times (6.24\times 10^{18}eV)[/tex]

[tex]Energy=2.10eV[/tex]

The energy of yellow peak is [tex]2.10eV[/tex]

Part 2:

Given:

Wavelength of blue peak = [tex]436nm=436\times 10^{-9}m[/tex]

Conversion used : [tex]1nm=10^{-9}m[/tex]

First we have to calculate the frequency of blue peak.

Formula used :

[tex]\nu=\frac{c}{\lambda}[/tex]

where,

[tex]\nu[/tex] = frequency of blue peak

[tex]\lambda[/tex] = wavelength of blue peak

c = speed of light = [tex]3\times 10^8m/s[/tex]

Now put all the given values in the above formula, we get:

[tex]\nu=\frac{3\times 10^8m/s}{436\times 10^{-9}m}[/tex]

[tex]\nu=6.88\times 10^{14}s^{-1}=6.88\times 10^{14}Hz[/tex] [tex](1Hz=1s^{-1})[/tex]

The frequency of blue peak is, [tex]6.88\times 10^{14}Hz[/tex]

Now we have to calculate the energy of blue peak.

Formula used :

[tex]E=h\times \nu[/tex]

where,

[tex]\nu[/tex] = frequency of blue peak

h = Planck's constant = [tex]6.626\times 10^{-34}Js[/tex]

Now put all the given values in the above formula, we get:

[tex]E=(6.626\times 10^{-34}Js)\times (6.88\times 10^{14}s^{-1})[/tex]

[tex]E=4.56\times 10^{-19}J[/tex]

Also,  

[tex]1J=6.24\times 10^{18}eV[/tex]

So,  

[tex]Energy=(4.56\times 10^{-19})\times (6.24\times 10^{18}eV)[/tex]

[tex]Energy=2.84eV[/tex]

The energy of blue peak is [tex]2.84eV[/tex]