Question

A laser pulse with wavelength 532 nm contains 3.85 mj of energy. how many photons are in the laser pulse?

Answer 1

Answer: 1.04 × 10¹⁶ photons

Explanation:

1) Data:

• E = 3.85mJj (mili joules) = 3.85×10⁻³ J

• λ = 532 nm = 532 × 10⁻⁹ m

• number of photons ?

2) Physical principles

a) The energy of a photon is given by the equation E = hν.

Where:

• h is Planck's constant 6.62607004 × 10⁻³⁴ J×s
• ν is the freguency of the light

b) The wavelength, λ, and the frequency, are related by the equation:

• ν = c / λ, where c is the speed of light at vacuum, approximately 3.0 × 10⁸ m/s

3) Solution:

• ν = c / λ = 3.0 × 10⁸ m/s / (538 nm) × 10⁹ nm/m = 5.576×10¹⁴ Hz

• E = hν = 6.62607004 × 10⁻³⁴ J×s s × 5.576×10¹⁴ Hz = 3.69 × 10 ⁻¹⁹ J

• Divide the total energy by the energy of one photon to find the number of photons:

         3.85×10⁻³ J / 3.69 × 10 ⁻¹⁹ J-photon = 1.04 × 10¹⁶ photons ← answer

Answer 2

The number of photons that are in the laser pulse is about :

1.03 × 10¹⁶ photons

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Further explanation

The term of package of electromagnetic wave radiation energy was first introduced by Max Planck. He termed it with photons with the magnitude is:

$\large {\boxed {E = h \times f}}$

E = Energi of A Photon ( Joule )

h = Planck's Constant ( 6.63 × 10⁻³⁴ Js )

f = Frequency of Eletromagnetic Wave ( Hz )

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The photoelectric effect is an effect in which electrons are released from the metal surface when illuminated by electromagnetic waves with large enough of radiation energy.

$\large {\boxed {E = \frac{1}{2}mv^2 + \Phi}}$

$\large {\boxed {E = qV + \Phi}}$

E = Energi of A Photon ( Joule )

m = Mass of an Electron ( kg )

v = Electron Release Speed ( m/s )

Ф = Work Function of Metal ( Joule )

q = Charge of an Electron ( Coulomb )

V = Stopping Potential ( Volt )

Let us now tackle the problem!

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Given:

wavelength = λ = 532 nm = 532 × 10⁻⁹ m

energy = E = 3.85 mJ = 3.85 × 10⁻³ J

Asked:

number of photons = N = ?

Solution:

$E = N h f$

$E = N h \frac { c }{ \lambda }$

$3.85 \times 10^{-3} = N \times 6.63 \times 10^{-34} \times \frac{3 \times 10^8}{ 532 \times 10^{-9} }$

$\boxed{N \approx 1.03 \times 10^{16}}$

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Learn more

• Photoelectric Effect : brainly.com/question/1408276

• Statements about the Photoelectric Effect : brainly.com/question/9260704

• Rutherford model and Photoelecric Effect : brainly.com/question/1458544
• Photoelectric Threshold Wavelength : brainly.com/question/10015690

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Answer details

Grade: High School

Subject: Physics

Chapter: Quantum Physics