Answer :
Number of photons are 241.935 ˣ10²⁰ which emitted per second by a helium neon laser having power output of 7.7mw.
We need to find the number of photons, and we know that power if defined as the division of energy with time. In other words,
Power=Energy/Time
where Energy is energy of light
and time is time taken by light to travel.
So,P=E/t
we know that energy of photons is given by the relation =hc/λ where h is plank's constant having value = 6.6 ˣ 10⁻³⁴(J-sec) /m ,c is speed of light having value 3 ˣ 10⁸m/sec and λ is the wavelength of light having value =632.8 ˣ 10⁻⁹m
So,putting the values ,we get
=>E= (6.6 ˣ 10⁻³⁴ ˣ 3 ˣ 10⁸) / 632.8 ˣ 10⁻⁹
=>E=(19.8 ˣ 10⁻²⁶) / 632.8 ˣ 10⁻⁹
=>E=0.031 ˣ 10⁻¹⁷J
Now,putting this energy value in power formula for 1 sec,we get
=>Power=0.031 ˣ 10⁻¹⁷J/1sec=0.031 ˣ 10⁻¹⁷Watt.
Now,we need to find the number of photons,we need to take division of powers,we get
=>Number of photons=(7.5 ˣ 10³W) / 0.031 ˣ 10⁻¹⁷W
=>Number of photons = 241.935 ˣ10²⁰
Hence, number of photons are 241.935 ˣ10²⁰
To know more about photons, visit here:
https://brainly.com/question/20912241
#SPJ4
(Complete question) is:
a helium-neon laser emits light of wavelength 632.8 nm and has a power output of 7.5 mw. how many photons are emitted per second by this laser? (plank's constant h is 6.6 ˣ 10⁻³⁴(J-sec) /m)
