Photons and Electrons

Question 1

Frequency

Answer 1

The number of complete waves that pass a point per second. Frequency is measured in hertz (Hz)

Question 2

Wavelength

Answer 2

The distance between two consecutive points on a wave that are in phase. Wavelength is measured in metres.

Question 3

The photoelectric effect

Answer 3

The process that occurs when light shines on a metal and electrons are ejected

Question 4

Significance of the photoelectric effect

Answer 4

It established the quantum theory and it illustrates the particle nature of light

Question 5

A photon

Answer 5

A quantum of energy when the energy is in the form of electromagnetic radiation

Question 6

Threshold frequency

Answer 6

The minimum frequency of incident radiation at which electrons will be emitted from a particular metal

Question 7

Work function

Answer 7

The minimum amount of energy required to emit an electron from the surface of a metal.

Question 8

Red shift

Answer 8

A shift in the spectra of distant galaxies toward longer wavelength i.e. towards the red end of the spectrum

Question 9

Absorption spectrum

Answer 9

Produced when white light from a source passes through a “cool” gas. It is also referred to as a line absorption spectrum

Question 10

Emission spectrum

Answer 10

Produced when electrons “fall” from an orbital of higher energy to an orbital of lower energy. It is also referred to as a line emission spectrum