Question

A discharge lamp rated at 25 W (1 W = 1 J/s) emits yellow light of wavelength 580 nm. How many photons of yellow light does the lamp generate in 1.0 s?

Answer 1

the number of photons of yellow light does the lamp generate in 1.0 s is 7 x
`10^(19)`

Step-by-step explanation:

given information:

power, P = 25 W

wavelength. λ - 580 nm = 5.80 x
`10^(-7)` m

time, t = 1 s

to calculate the number of photon(N), we use the following equation

N = λPt/hc

where

λ = wavelength (m)

P = power (W)

t = time interval (s)

h = Planck's constant (6.23 x
`10^(-34)` Js)

c = light's velocity (3 x
`10^(8) m/s^(2)`)

So,

N = λPt/hc

= (5.80 x
`10^(-7)`)(25)(1)/(6.23 x
`10^(-34)`)(3 x
`10^(8) m/s^(2)`)

= 7 x
`10^(19)`