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A 100 W point source emits monochromatic...

A 100 W point source emits monochromatic light of wavelength `6000 A`
Q. Calculate the photon flux (in SI unit) at a distance of 5m from the source. Given `h=6.6xx10^(34)`J s and `c=3xx10^(8)ms^(-1)`

A

`10^(15)`

B

`10^(18)`

C

`10^(20)`

D

`10^(22)`

Text Solution

Verified by Experts

The correct Answer is:
B
Intensity (i.e., energy flux) at a distance of 5m from the source of power P,
`I=(P)/(4pir^2)=(100)/(4pixx5^2)=(1)/(pi)(W)/(m^2)`
The number of photons passing normally per unit area per second i.e.,
Photon flux `=(I)/(E)=((1)/(pi))/(3.3xx10^(-19))approx10^(18)` photons `m^(-2)s^(-1)`
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Knowledge Check

  • A 100 W point source emits monochromatic light of wavelength 6000 A Calculate the total number of photons emitted by the source per second.

    A
    `5xx10^(20)`
    B
    `8xx10^(20)`
    C
    `6xx10^(21)`
    D
    `3xx10^(20)`

  • A 160 watt light source is radiating light of wavelength 6200 Å uniformly in all directions. The photon flux at a distance of 1.8 m is of the order of (Planck's constant 6.63xx 10^(-34) J-s)

    A
    `10^(2)m^(-2)s^(-1)`
    B
    `10^(12)m^(-2)s^(-1)`
    C
    `10^(19)m^(-2)s^(-1)`
    D
    `10^(25)m^(-2)s^(-1)`

  • A 160 watt light source is radiating light of wavelength 6200 Å uniformly in all directions. The photon flux at a distance of 1.8 m is of the order of (Plank's constant 6.62 xx 10^(-34) J-s )

    A
    `10^(2) m^(-2)s^(-1)`
    B
    `10^(12) m^(-2)s^(-1)`
    C
    `10^(19) m^(-2) s^(-1)`
    D
    `10^(25) m^(-2) s^(-1)`

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