Optical Phenomena and Properties of Materials

Question 1

photoelectric effect

Answer 1

the process whereby electrons are ejected from a

metal surface when light of suitable frequency is incident on that surface.

Question 2

Threshold frequency

Answer 2

As the minimum frequency of light needed to emit

electrons from a certain metal surface

Question 3

Work function

Answer 3

The minimum energy that an electron in the metal needs to be emitted from the metal surface.

Question 4

Explain the formation of atomic spectra by referring to energy transition.

Answer 4

An atomic absorption spectrum is formed when certain frequencies of electromagnetic radiation passing through a substance is absorbed.
For example, when light passes through a cold gas, atoms in the gas absorb characteristic frequencies of the light and the spectrum observed is a continuous spectrum with dark lines where characteristic frequencies of light were removed. The frequencies of the absorption lines are unique to the type of atoms in the gas.

Question 5

Atomic emission spectrum

Answer 5

Is formed when certain frequencies of
e electromagnetic radiation are emitted due to an atom making a transition from a higher energy state to a lower energy state.
For example, atoms in a hot gas emit light at characteristic frequencies. The spectrum observed is a line spectrum with only a few coloured lines of frequencies unique to the type of atom that is producing the emission lines