Question

If 5% of the energy supplied to a bulb is radiated as visible light, the number of visible quanta emitted per second by a 100W bullb, assuming the wavelength of visible light to be 5.6×10⁻⁵ cm, is___

o 1.4 x 10¹⁹
o 1.4 x 10²⁰
o 2.4 x 10¹⁹
o 2 x 10²⁰

Answer 1

The number of visible quanta emitted per second by a 100W bulb can be calculated by dividing the power of the bulb by the energy per photon. Option 3 is correct.

Step-by-step explanation:

The number of visible quanta emitted per second by a 100W bulb can be calculated using the formula:

Number of photons emitted per second = (Power of bulb) / (Energy per photon)

First, convert the power of the bulb from watts to joules per second by multiplying it by 1.0, since 1 watt is equal to 1.0 joule per second. So, the power of the bulb is 100 J/s. Next, find the energy per photon by using the formula:

Energy per photon = (Planck's constant × speed of light) / (wavelength of visible light)

Substituting the values, we get:

Energy per photon = (6.63 × 10^-34 J·s × 3.00 × 10^8 m/s) / (5.6 × 10^-5 cm)

Calculating this value, we find the energy per photon is approximately 3.94 × 10^-19 J.

Finally, we can calculate the number of photons emitted per second:

Number of photons emitted per second = (Power of bulb) / (Energy per photon) = (100 J/s) / (3.94 × 10^-19 J) ≈ 2.54 × 10^20

Therefore, the correct answer is 2.54 x 10^19.