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How many photons are emitted per second ...

How many photons are emitted per second by a 5m W laser source operating at 632.8nm?

Text Solution

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The energy of each photon is
` E = (hc/lambda)`
` = ((6.63 xx (10^-34)J s) xx (3 xx (10^8)m (s^-1))/ (632.8 xx (10^-9)m))`
` = (3.14 xx (10^-9)m).`
The energy of the laser emitted per second is
` (5 xx (10^-3)J). Thus the number of photons emitted per`
second
` (5 xx (10^-3)J/ 3.14 xx (10^-19)J) = 1.6 xx (10^16).
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Knowledge Check

  • How many photons are emitted per second by a 5 mW laser source operating at 632.8 nm?

    A
    `1.6xx10^(16)`
    B
    `1.6xx10^(13)`
    C
    `1.6xx10^(10)`
    D
    `1.6xx10^(3)`

  • How many photons are emitted by a laser source of 5 xx 10^(-3) W operating at 632.2 nm in 2 second (h = 6.63 xx 10^(-34)Js) ?

    A
    `3.2 xx 10^(16)`
    B
    `1.6 xx 10^(16)`
    C
    `4 xx 10^(16)`
    D
    None of these

  • The number of photons emitted per second by a 60 W source of monochromatic light of wavelength 663 nm is: (h=6.63xx10^(-34)Js )

    A
    `4xx10^(-20)`
    B
    `1.5xx10^(20)`
    C
    `2xx10^(-20)`
    D
    `2xx10^(20)`

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