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 metal and electrons are ejected.

Question 4

Significance of the photoelectric effect

Answer 4

It establishes the quantum theory and it illustrates the particle nature of light.

Question 5

A photon

Answer 5

The 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

The work function of a metal

Answer 7

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

Question 8

Redshift

Answer 8

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

Question 9

An 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

An 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.