Flashcards in Quantum Mechanics Deck (23)

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1

## The the very small subatomic level things behave as both what?

### Particles (they have momentum) and waves (they diffract, refract, etc.).

2

## An electron has a mass (9.11x10^-31 kg) but a beam of electrons does what that’s wave like?

### Diffracts through a a gap.

3

## Light is a wave propagated by what?

### Oscillations in the electric and magnetic fields.

4

## If light is a wave what properties are explained?

### Diffraction, refraction, etc.

5

## What is a particle of light called?

### A photon.

6

## The de Broglie equation:

###
λ=h/mv or λ=h/p

Where:

λ is wavelength, m.

h is Planck’s constant, 6.63x10^-34 m^2kgs^-1 (Js).

p is momentum, kgms^-1 (m is mass, kg, v is velocity, ms^-1).

7

## What was the traditional idea in the 19th century of black bodies?

### They emit all frequencies of light equally and the higher the frequency of radiation the greater the energy.

8

## What was the problem with the 19th century idea that a black body gives off radiation evenly and the higher the frequency the more energy it emitted?

### When plotted the line tends to infinite energy which violates the conservation of energy principle. If a black body radiator had infinite energy it must be gaining energy from somewhere else.

9

## What was actually observed about black body radiators causing the ultraviolet catastrophe?

### Energy per unit frequency is still proportional to wavelength across the spectrum, however stars do not emit infinite amounts of light at the short wavelengths.

10

## Plank came up with a model of light for fitting the observations of the ultraviolet catastrophe. What does his law state?

### That electromagnetic radiation from heated bodies is not emitted as a continuous flow, but is made up of discrete units of energy or quanta.

11

## What does the size of quanta depend on?

### The fundamental physics constant, Planck’s Constant, 6.63x10^-34Js.

12

## Planck's Law equation:

###
E = hf

Where:

E is energy in J.

h is Planck's Constant, 6.63x10^-34 Js.

f is frequency in Hz.

13

## An electron falling down the energy levels releases a what?

### A photon.

14

## What can be said about the chance of an electron falling down multiple energy levels at once as opposed to single step falls?

### An electron falling down multiple steps at once is less likely than single step falls down the energy levels.

15

## Electrons can only exist in discrete what around an atom?

### Energy levels.

16

## What happens if you fire infrared radiation at a negatively charged plate?

### No electrons will be liberated no matter how intense the radiation is?

17

## What happens if you fire ultraviolet radiation at a negatively charged plate?

### Electrons will be liberated with increasing rate if the intensity is increased.

18

## One photon can only liberate one what in the photoelectric effect and what is it liberated as?

### An electron and it is liberated as a photoelectron.

19

## Equation for the photoelectric effect:

###
hf = Φ + Eu

Where:

hf is the energy of the photon in J.

Φ is the work function of the material in J.

Eu is the energy of the photoelectron once free in J.

20

## What is 1eV in J?

### 1.6x10^-19 J

21

## What is 1J in eV?

### 6.25x10^18 eV.

22

## How do we convert between eV and J and vice versa?

###
If J into eV divide by 1.6x10^-19.

If eV into J multiply by 1.6x10^-19.

23