Question

A 100 watt bulb emits monochromatic light of wavelength 400nm calculate the no of photons emitted per minute in the bulb

Answer 1

Answer :

Given -

• Power of bulb = 100 watt
• Wavelength = 400 nm

To Find -

• The number of photons emitted per second by the bulb.

Solution -

Power of the bulb = 100 J s^{-1}

Energy of one photon = E = hv = hc/λ

⇒ (6.626 × 10^{-34} × 3 × 10⁸)/(400 × 10^{-9})

⇒ 4.969 × 10^{-19} J

Number of photons emitted :

⇒ (100)/(4.969 × 10^{-19})

⇒ 2.012 × 10²⁰ s^{-1}

Hence, The number of photons emitted per second by the bulb = 2.012 × 10²⁰ s^{-1}.