The Electron

Question 1

Thermionic Emission

Answer 1

Thermionic emission is the giving off of electrons from the surface of a hot metal

Question 2

Cathode Rays

Answer 2

Streams of high speed electrons moving from the cathode are called cathode rays

Question 3

The Electronvolt

Answer 3

The electronvolt (eV) is the amount of energy gained or lost by an electron when it moves through a potential difference of one volt

Question 4

Movement of a Beam of Electrons in a Magnetic Field

Answer 4

A beam of electrons moving at right angles to a magnetic field moves in a circle

Question 5

The Photoelectric Effect

Answer 5

The photoelectric effect is the emission of electrons from the surface of a metal by electromagnetic radiation of a suitable frequency

Question 6

Relationship Between Photocurrent and Light in a Photocell

Answer 6

The photocurrent is directly proportional to the intensity of the light

Question 7

Threshold Frequency

Answer 7

For a given metal the frequency below which photoemission will not occur is called the threshold frequency. Light of frequency above the threshold frequency will cause photoemission

Question 8

Work Function

Answer 8

The work function of a metal is the minimum energy needed to remove the loosest electron from the surface of that metal

Question 9

Photon

Answer 9

A photon is a packet of electromagnetic energy. The energy E of a photon is given by E = hf, where f is its frequency and h is Planck’s constant

Question 10

X-Rays

Answer 10

X-rays are high frequency electromagnetic radiation produced when high speed electrons in a cathode ray tube strike a metal target that has high melting point