A 100 W incandescent lightbulb emits about 5 W of visible light. (The other 95 W are emitted as infrared radiation or lost as he

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A 100 W incandescent lightbulb emits about 5 W of visible light. (The other 95 W are emitted as infrared radiation or lost as he

at to the surroundings.) The average wavelength of the visible light is about 600 nm, so make the simplifying assumption that all the light has this wavelength. How many visible-light photons does the bulb emit per second?

Physics

1 answer:

kicyunya [3.2K] · Answer 1 · 2026-03-12T10:03:58+03:00

Answer:

n = 1.89 x 10¹⁹ photons per second.

Explanation:

Given values:

Power of the bulb = 100 W

Visible light output = 5 W

Wavelength of visible light = 600 nm

Calculating the number of photons emitted each second:

Using the wavelength formula:

$\lambda = \dfrac{c}{\nu}$

$\nu= \dfrac{c}{\lambda}$

$\nu= \dfrac{3 \times 10^8}{600 \times 10^{-9}}$

$\nu=5 \times 10^{14}\ Hz$

Photon energy:

U = h υ

U = 6.63 x 10⁻³⁴ × 4 x 10¹⁴

U = 2.65 x 10⁻¹⁹ J

Determining the number of photons:

$n = \dfrac{P}{U}$

$n = \dfrac{5}{2.65 \times 10^{-19}}$

n = 1.89 x 10¹⁹ photons/s.