Question

Neon is used in sign board if it emits energy at 616nm calculate
A) frequency of emission?
B) distance traveled by this radiation in 30sec?
C) energy of quantum ?
D) no.of quantas present if it produces two joules of energy ?

Answer 1

Given :
Wavelength =λ=616nm = 616 x 10 ⁻⁹m

A) frequency of emission:
Frequency = ν= C/λ = 3x 10⁸ m/s / 616 x 10 ⁻⁹m =4.87x 10 ¹⁴ / s

B]distance traveled by this radiation in 30sec :
 Speed of light = 3x 10⁸m/s
time= 30 sec
Speed= Distance /time
Distane travelled= 3x 10⁸x30 = 9x10⁹m

c]Energy of quantum:
E=hν=hc/λ where
h= Planks Constant = 6.62x 10⁻³⁴ Js
E= 6.62x 10⁻³⁴ x3x 10⁸/ 616 x 10 ⁻⁹
=32.27 x 10⁻²⁰ J

d] Number of Quanta present in 2 joules of energy:
=2J/32.27 x 10⁻²⁰

=6.2 x 10¹⁸