# (solved)Question 2.11 of NCERT Class XI Chemistry Chapter 2

A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.

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### Question 2.11 NCERT Class XI Chemistry

A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.

### Video Explanation(detailed solution given after this video)

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### Solution in Detail

by Planck's equation energy E of n quanta

$\displaystyle E = n \times \frac{hc}{\lambda}$

$\displaystyle \implies n = \frac{E \lambda}{hc}$

Energy by bulb = 25 W = 25 J/s

$\displaystyle \therefore n = \frac{25 \text{(J/s)} \times (0.57 \times 10^{-6} \text{ (m)})}{6.6 \times 10^{-34}\text{ (Js)} \times 3 \times 10^8\text{ m/s}}$

$\displaystyle = 7.19 \times 10^{19} \text{quanta/s}$