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 establishes the quantum theory and it illustrates the

particle nature of light.

Question 5

Photon

Answer 5

The quantum of energy when the energy is in the form of electromagnetic radiation.

Question 6

Threshold frequency (f0):

Answer 6

The minimum frequency of incident radiation at which electrons will

be emitted from a particular metal.

Question 7

Work function of a metal (W0):

Answer 7

The minimum amount of energy needed 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 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.