Question

Violet light has a wavelength of about 410 nm.

a. What is its frequency?

b. Calculate the energy of one photon of violet light

c. What is the energy of 1.0 mol of violet photons (hint: 1 mol=6.02*10^23)

d. Compare the energy of photons of violet light with those of red light (700nm). Which has the greater energy?

Answer 1

a)

Given:

lambda = 4.1*10^-7 m

use:

f = c/lambda

=(3.0*10^8 m/s)/(4.1*10^-7 m)

= 7.317*10^14 Hz

Answer: 7.32*10^14 Hz

b)

Given:

lambda = 4.1*10^-7 m

use:

E = h*c/lambda

=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(4.1*10^-7 m)

= 4.848*10^-19 J

Answer: 4.85*10^-19 J

c)

Energy of 1 mol = energy of 1 photon * Avogadro's number

= 4.848*10^-19*6.02*10^23 J/mol

= 2.92*10^5 J

= 2.92*10^2 KJ

Answer: 292 KJ

d)

E = h*c/lambda

so,

the one with smaller wavelength will have greater energy.

Wavelength is smaller for violet and hence it has higher energy.

Answer: violet