The photoelectric effect – Evidence for the particle-like nature of light

Question 1

Electron-volt

Answer 1

electron-volt a measure of energy equal to 1.6 × 10−19 J, derived from the loss or gain of energy by an electron moving across a potential difference of 1 volt

Question 2

Photocurrent

Answer 2

photocurrent the electrical current produced by photoelectrons in the photoelectric effect

Question 3

Photoelectrons

Answer 3

photoelectrons electrons emitted in the photoelectric effect

Question 4

Stopping voltage

Answer 4

stopping voltage the reverse potential that repels the most energetic electrons from the collector electrode and causes the photocurrent to become zero. It has the same numerical value as the maximum kinetic energy of emitted electrons in electron-volts

Question 5

The Work function and how to find it on a graph and its equation

Answer 5

work function the minimum energy of light required to release the most loosely bound electron from a metal surface.

Essietially the work functiom the amount of energy required to release the most loosely bound electron from a metal.

To find on a graph simply solve for c (mx+c) or distance on y axis.

KE_max = light energy delivered to each electron − Φ

Question 6

Planck’s Constant

Answer 6

Planck’s constant a constant equal to 6.63 × 10^−34 J s or 4.14 × 10^−15 eV s

Question 7

Threshold frequency

Answer 7

Threshold frequency the minimum frequency of light at which electrons are ejected from a metal surface in the photoelectric effect

Question 8

Discrete

Answer 8

discrete limited to certain values (not continuous)

Question 9

Particles

Answer 9

particle a theoretical object that is discrete and has a defined location

Question 10

Photon

Answer 10

photon a particle of light with a discrete amount of energy

Question 11

Photoelectric effect

Answer 11

The photoelectric effect describes how light is able to free electrons, called photoelectrons, from a metal surface to produce a photocurrent.

Question 12

Converstion of electron volts to joules

Answer 12

Question 13

What occurs when the intesnity of light is increased?

Answer 13

When you increase the intensity of light, the photocurrent increased but the kinetic energy of the electron stays the same.

Question 14

What occurs when freuqnecy is manipulated in relation to the photoelectric effect?

Answer 14

There is a minimun frequency below which no photocurrent is measured (no movement of electrons).

Above this frequency the kinetic energy of the electrons increase with the frequency. The photocurrent is not affected by the increase in frequency.

Question 15

Explain the effect of changing the density of light. Current vs voltage graph

Answer 15

When the intensity of light incident on the metal surface is increased, more electrons are emitted every second. As such, an increase in the intensity of the light causes an increase in the maximum current.

Similarly, a decrease in the intensity of light causes a decrease in the maximum current.

Changing the intensity of light does not change the stopping voltage and therefore it does not change the kinetic energy of photoelectrons (assuming frequency is constant).

Question 16

What does the photoelectroc effect demonstrate?

Answer 16

The photoelectric effect demonstrates the effect that light striking a metal surface is able to free electrons from the metal.

The electrons released are known as photoelectrons and their movement produces a current known as the photocurrent.

Question 17

Cathodes and Anodes in relation to the photoelectric effect

Answer 17

A cathode is a material that flows a current. In the photoelecrtice effect the cathode is the metal surface.

An anode is is the terminal where current flows in from outside. Where the elecrtons from the metal surface travel to a collector electrode or anode.

Question 18

Diagram of a Photoelectric setup regarding a cathode and anode.

Answer 18

Question 19

Dependent and independent variables of the photoelectric effect experiment

Answer 19

The independent variables of the photoelectric effect experiment are:

• the intensity of light (brightness).
• the frequency of light (colour, when in the visible range)

The dependent variables of the photoelectric effect experiment are:

• the photocurrent.
• the maximum kinetic energy of electrons (KE_max).

Question 20

What does the Photocurrent-potential graph features represent?

Answer 20

Question 21

What does the photoelecrtic effect display on Kinetic energy-frequency graphs

Answer 21