Lecture 3:Wave nature of electromagnetic radiation ; Plank’s quantum theory ; Photoelectric effect ; Atomic spectra

What is emission and absorption spectra?

Name the scientist who demonstrated photoelectric effect experiment.

What is threshold frequency?

Define photoelectric effect.

On what frequency does the frequency from a black body depend?

What did Planck’s theory explain?

The quantum numbers of six electrons are given below. Arrange them in order of increasing energies. If any of these combination(s) has/have the same energy lists:

1. n= 4, l = 2, ml= -2 , ms= -1/2

2. n= 3, l = 2, ml= 1 , ms= +1/2

3. n= 4, l = 1, ml= 0 , ms= +1/2

4. n = 3, l= 2, ml= -2 , ms= -1/2

5. n = 3, l= 1, ml= -1 , ms= +1/2

6. n = 4, l= 1, ml= 0 , ms= +1/2

Emission transitions in the Paschen series end at orbit n= 3 and start from orbit n and can be represented as v = 3.29 x 10¹⁵(Hz) [1/3²- 1/n²]

Calculate the value of nif the transition is observed at 1285 nm. Find the region of the spectrum.

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. Calculate the ionisation energy of sodium in kJ mol^-1

What is the number of photons of light with a wavelength of 4000 pm that provide

Calculate the wavelength, frequency and wave number of a light wave whose period is 2.0 x 10^-10s.

Find energy of each of the photons which

(i) correspond to light of frequency 3 x 10¹⁵ Hz.

(ii) have wavelength of 0.50 Ô¦.