Question

wave length 300 nm and k.e 1.6×10 5 j find minimum energy​

Answer 1

Given:

wavelength =300nm=300x 10⁻⁹m

h=planks constant=6.62 x 10⁻³⁴Js

c=velocity of light =3x10⁸ m/s

E=hv=hc/λ

⇒(6.62 x 10⁻³⁴ x3x10⁸)/300x 10⁻⁹

=6.62 x 10⁻⁹J

so, Kinetic energy for for 1 mole of photons=6.62 x 10⁻⁹ x6.022 x 10²³

=3.99x 10⁵J

so ,minimum amount of energy required to remove 1 mole of electrons from sodium atoms is

=(3.99 x 10 ⁵)- (1.68 x 10⁵)

=2.31 x 10 ⁵J

∴ minimum energy required to remove 1 electron from Na atom=

⇒2.31 x 10⁵/6.022 x 10²³

⇒3.84 x 10⁻¹⁹ J