Quantum

Question 1

State the equations to find energy of a photon

Answer 1

E = hf
E = hc / lambda

Question 2

What is a photon?

Answer 2

A discrete packet of energy

Question 3

State the base unit of h

Answer 3

kgm2s-1

Question 4

Define an electronvolt

Answer 4

the energy aquired by an electron when it passes through a potential difference of 1V

Question 5

What is the photoelectric effect?

Answer 5

An effect that occurs when a photon of sufficient energy interacts with the surface of a metal and releases a photoelectron from the surface

Question 6

State and explain the proof for the particulate nature of EM radiation

Answer 6

photoelectric effect - the emission occurs instantly whereas the wave theory predicts that the emission would take time

Question 7

define the work function

Answer 7

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

Question 8

define threshold frequency

Answer 8

the minimum photon frequency required to release a photon from the surface of a metal

Question 9

state the equation for the work function

Answer 9

h x f0

Question 10

describe the photoelectric effect

Answer 10

1. If energy of photon > work function an electron will be emitted
2. If the energy of the photon < work function, no electrons are emitted
3. There is a one to one electrons and photons

Question 11

Why are no electrons emitted with low energy photons?

Answer 11

We can never get more than 1 photon interacting with an electron and releasing it so if the photon energy is not sufficient no electrons are released

Question 12

Describe the gold leaf electroscope experiment

Answer 12

1. Electroscope is charges with a plastic rod
2. Charge is accumulated on the surface of the zinc plate and on the gold leaf electroscope
3. Due to electrostatic repulsion the gold leaf rises

Question 13

State 3 conclusions of the photoelectric effect

Answer 13

1. The emission of photons depends only on the frequency of the light, not on the intensity
2. The electron emission is almost instantaneous, which means EM radiation has particle nature
3. There is a one to one interaction between electrons and photons

Question 14

Why is there maximum kinetic energy?

Answer 14

Most electrons require more energy than the work function to escape the surface of the metal

Question 15

State Einstein equation

Answer 15

hf = work function + KEmax

Question 16

State De Broglie’s wavelength

Answer 16

h / p
h / mv