Physics, asked by alreya, 3 months ago


For wave intensity 1 W/m2 and wavelength 1 µm in vaccum, find the number of photons. What is the energy of photon of wavelength 1 mm? Compare this with the characteristic thermal energy at 3000 K.



Answers

Answered by Anonymous
5

Answer:

Hey Mate..!

Explanation:

eV(Ionisation energy)=133.24×10

−16

J

We use the formula

eV=hf                   (Eq 1)

where eV is the ionisation energy

h is the Planck's constant=6.62×10

−34

f is the frequency f=

λ

C

Where C is the speed of light C=3×10

8

msec

−1

λ is the wavelength

Putting the value of f in equation 1

eV=h

λ

C

133.24×10

−16

=

λ

6.62×10

−34

×3×10

8

λ=1.49×10

−11

m

For the second question

K=hv−hv

0

                            (eq 1)

where h is the Planck's constant and v

0

is the threshold frequency and hv

0

is the work function and K is the kinetic energy

v=

λ

C

Putting the values in euation 1

1=

λ

hC

−hv

0

    (eq 2)

4=

λ

3hC

−hv

0

    (eq 3)

eq 2 is multiplied by −3 then adding eq 3 from eq2

−3=

λ

−3hC

+3hv

0

4=

λ

3hC

−hv

0

    

4−3=(3−1)hv

0

hv

0

=0.5eV

0

Answered by ShreyaNegi02
0

Answer:

a) Number of photons in vacuum = 5.03×10¹⁸    

b) Energy of photon of wavelength 1mm = 19.878×10⁻²³ joule

Explanation:

Given:            intensity of wave is = 1W/m²     

                wavelength in vacuum= 1μm

To calculate number of photon :       

   number of photon in vacuum =  total energy / energy of each photon     energy of each photon

b   (E) = hν    

     E = hc/λ

     h = 6.626×10⁻³⁴ js  

    c =3×10⁸ m/s²  

     λ= 1×10⁻⁶ m    

 E = (6.626×10 ⁻³⁴)(3×10⁸)/(1×10⁻⁶)      

      E =  19.88×10 ⁻²⁰

total energy =  1w

number of photon =  1/(19.88×10⁻²⁰)

 number of photon in vacuum  = 5.03×10¹⁸

Energy of photon of λ = 1mm  :   

λ= 1mm = 1×10⁻³ m  

 E= hc/λ  

 E = (6.626×10⁻³⁴)(3×10⁸)/(1×10⁻³)  

 E = 19.87×10⁻²³ j

Thermal energy:  

 E = kT

  Boltzmann constant (k)= 1.38×10⁻²³  

 temperature (T)= 3000K  

 E =(1.38 ×10⁻²³)(3000)  

 E = 4140×10⁻²³ j

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