A special kind of light bulb emits monochromatic light of wavelength 630 nm. Electrical energy supplied to it at the rate of 60W, and the bulb is 93% efficient at converting that energy into light energy. How many photons are emitted by the bulb during its life time of 730h?

The correct answer should be numberphotons*hc/lambda=.93*60*730*3600 because the 93% efficiency applies to the bulb and not the energy per photons.

Power=energy/time

If power is 60 watt that is 60 joule per second.

Energy emitted for 730 hrs=60*730*60*60=157680000J

93 percent of total emitted energy=0.93*157680000=146642400J

Energy of single photon =hc/lambda=3.155*10 pow(-19)

Then no:of photons emitted by the bulb during its life time of 730hr =146642400/3.155*10pow(-19)
=4.64*10pow(26)photons.
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To calculate the number of photons emitted by the light bulb, we need to find the energy of each photon and then calculate the total energy emitted by the bulb.

1. First, we need to determine the energy of each photon using the formula:

E = hc / λ

Where:
E is the energy of a photon
h is Planck's constant (6.626 x 10^-34 Js)
c is the speed of light (3 x 10^8 m/s)
λ is the wavelength of light (630 nm = 630 x 10^-9 m)

Plugging in the values, we get:

E = (6.626 x 10^-34 Js) × (3 x 10^8 m/s) / (630 x 10^-9 m)

Simplifying this expression, we find:

E ≈ 3.14 x 10^-19 J

2. Next, we need to calculate the total energy emitted by the bulb during its lifetime. We can do this by multiplying the power supplied by the bulb by the efficiency and the time period:

Total energy emitted = Power × Efficiency × Time

Plugging in the values, we get:

Total energy emitted = (60W) × (0.93) × (730h)

Simplifying this expression, we find:

Total energy emitted ≈ 39,078 J

3. Finally, we can calculate the number of photons emitted using the formula:

Number of photons = Total energy emitted / Energy of each photon

Plugging in the values, we get:

Number of photons ≈ (39,078 J) / (3.14 x 10^-19 J)

Simplifying this expression, we find:

Number of photons ≈ 1.24 x 10^26 photons

Therefore, the light bulb emits approximately 1.24 x 10^26 photons during its lifetime of 730 hours.

find the energy per photon (E=hc/Lambda)

find the total energy: 60*730*3600 watts

numberphotons*.93*hc/lambda=60*730*3600

solve for number photons

check my thinking.