Question

A sample of calcium is excited electrically, resulting in the emission of light with energy 3.09*10^-19 J per atom

a. Calculate the frequency of this light in hertz (Hz).

b. Calculate the wavelength of this light (in nm).

c. using a visible spectrum, identify the color of this light

Answer 1

We know the Planks equation

E = hf

Where

E = energy = 3.09 x 10^-19 J/atom

h = Planks constant = 6.626 x 10^-34 J.s

f = frequency

So

Frequency f = E/h

= 3.09 x 10^-19 J/atom / 6.626 x 10^-34 J.s

= 4.66 x 10¹⁴ Hz

b.)

Wawelength can be calclate from the formula

E = hc/w

Where

E = energy = 3.09 x 10^-19 J/atom

h = Planks constant = 6.626 x 10^-34 J.s

c= speed of light = 3 x 10⁸ m/s

w = wavelength

So

Wavelength w = hc/E

= 6.626 x 10^-34 J.s x 3 x 10⁸ m/s /3.09 x 10^-19 J/atom

= 643 x 10⁹ m = 643 nm

c)

The visible spectrum is between 400 nm (violet)
to about 700 nm (red) and light of wavelength 643 nm which falls
in the orange-red area of the spectrum