Unit 2 - Photons and Quantum Physics

Question 1

What is a photon?

Answer 1

A quantum/packet of light (or energy idk)

Question 2

What is an electron volt

Answer 2

the unit of energy equal to the work done when an electron is moved through a potential difference of 1 volt.

1 eV = 1.6x10⁻¹⁹ Joules

Question 3

What is the photoelectric effect?

Answer 3

Electrons can escape from the surfacec of certain metals if the surface of the metal is hit by the electromagnetic radiation (such as light) of sufficient frequency

Question 4

What are the 4 laws of photoelectric emission?

Answer 4

1) The number of electrons released from the surface is proportional to the intensity of the incident radiation

2) Emission occurs with no observable time lag.

3) The kinetic energy of the photoelectrons depends only on the frequency of the light and NOT on the intensity of the light.

4) There exists a threshold frequency of emission. When frequency is less than the threshold frequency, no photoelectrons sare emitted. Threshold frequency depends on the type of metal.
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(so baisicaly the threshold frequency is like a requirement type thing, and the frequency must be that or greater so the electrons can be emitted).

Question 5

Explain how the photoelectric effect works

Answer 5

The photons penetrates into the surface layer of the metal and imparts all of its energy to one electron in the material . Only 1 photon can interact with 1 electron. The intensity of light is proportional to number of photoelectrons. The electrons need a certain amount of energy to be released from the metal to gain zero energy. This is known as the work function of the metal.

(this is why there is a need for a threshold frequency)

Question 6

In photoelectric emission, if the photon has more than the minimum energy what can be observed?

Answer 6

The difference between the minimum energy and the photon’s energy is seen as kinetic energy of the photoelectron. This obeys the law of conservation of energy.

Question 7

Define the work function

Answer 7

the minimum energy required to release an electron from the surface of a metal.

Question 8

What is the threshold frequency

Answer 8

the minimum frequency required to release an electron from the surface of a metal.

Question 9

What is a vaccume photocell

Answer 9

a device which can be used to measure the maximum kinetic energy of electrons.

Question 10

What is a wave phenomenon

Answer 10

when laser light is passed through a diffraction grating a line of dots are obtained of the screen corresponding to the orders where constructive interference is seen.

Question 11

How do u demonstrate the photoelectric effect?

Answer 11

using a gold leaf electroscope

ion really know how it works