Chapters 9, 10, 11 And 12

Front 1

What is a photon?

Back 1

A particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.

Front 2

How are electromagnetic waves produced?

Back 2

Electromagnetic waves are produced by an oscillating charge. A changing electric field produces a changing magnetic field. EM waves oscillate in mutually perpendicular directions.

Front 3

Explain the oscillation of electric and magnetic field strength vectors.

Back 3

They oscillate perpendicular to each other.

Front 4

In what direction do electric field vectors oscillate?

Back 4

The electric field strength vector oscillates in a direction parallel to the wire carrying the oscillating charge.

Front 5

Electromagnetic waves are _________ waves.

Back 5

Traverse.

Front 6

In what direction do magnetic field vectors oscillate?

Back 6

The magnetic field strength vector oscillates in a direction perpendicular to the wire in which the charge is oscillating.

Front 7

An accelerating charged particle radiates a what?

Back 7

It radiates an electromagnetic wave.

Front 8

What is the relationship between the frequency of oscillation and the frequency of an electromagnetic wave?

Back 8

The frequency of a radiated electromagnetic wave is the same as the frequency of oscillation of the charges which produces it.

Front 9

What are the metal rods on a set of antennae called?

Back 9

Dipoles.

Front 10

What must be connected to two dipoles to create an electromagnetic wave?

Back 10

An AC RF generator.

Front 11

How is an electromagnetic wave created for the transmission of television signals?

Back 11

An alternating current is produced through the dipoles creating a positive and negative end. The electric field moves in the direction of charge, (towards the negative). The current then switches direction to create a wave.

Front 12

What is meant by the propagation of a wave?

Back 12

It's direction. (e.g. left, right, into page, out of page).

Front 13

If a wave is propagating to the right, in which direction must the electric and magnetic fields be oscillating?

Back 13

The electric and magnetic fields are perpendicular to each other. They also oscillate perpendicular to the propagation.

Front 14

If a satellite is broadcasting waves in the horizontal plane, which direction must the receiving antenna be facing?

Back 14

In the horizontal plane as an alternating current must be made between the dipoles of the receiving antenna. (The plane of polarisation is horizontal).

Front 15

What is the equation of the speed of light?

Back 15

c=fλ

Front 16

Between what wavelength range is light visible to the human eye? Also, name the spectra which are above and below the visible range.

Back 16

Between approximately 400nm and 700nm. Red appears at the highest end while violet appears at the lowest end and hence, infrared appears near 700nm while ultraviolet appears near 400nm.

Front 17

What does the acronym "LADS" stand for?

Back 17

Laser Airborne Depth Sounder

Front 18

What is the LADS system used for?

Back 18

To find the depth of a certain body of water using laser pulses.

Front 19

Give three reasons why a powerful laser is needed in the LADS system.

Back 19

1) Turbid water, (water with scattered particles throughout), will tend to scatter light in all directions. This means less light will reach the ocean floor and therefore less light will be reflected to the plane.

2) Water tends to absorb light. Hence more powerful lasers are required to reach the bottom of the ocean and then reflect back without being absorbed. This is why green light is used as its frequency is absorbed the least in water.

3) The seabed also absorbs light meaning more energy is required to overcome this and hence allow reflections from the seabed.

Front 20

Define diffraction.

Back 20

The change in the direction of propagation of a wave as it passes by an obstacle while remaining in the same medium.

Front 21

Diffraction through a single narrow slit results in what? (Explain in terms of bright bands and intensity).

Back 21

On a screen, a wide central band of light in the centre with narrower bands on each side is seen. The central band has the most intensity and this decreases rapidly as the bands increase outwards.

Front 22

What is meant by the term, "two wave sources are in phase"?

Back 22

Two wave sources are in phase if the emitting waves are in phase. That is, if one wave emits a crest, the other will emit a crest at the same time and so on.

Front 23

What is meant by the term, "monochromatic light"?

Back 23

A light source with a single frequency of light being emitted. (Used in Young's Double Slit experiment).

Front 24

If one were to say that two waves were coherent, what would one be meaning?

Back 24

That the two waves are maintaining a constant phase relationship with each other. They must be producing waves of the same type and of the same frequency.

Front 25

Which two things are incandescent globes not?

Back 25

They are not:

1) Coherent

2) Monochromatic

Front 26

If there is constructive interference happening between two waves, what are they doing to each other?

Back 26

Reinforcing each other.

Front 27

If there is destructive interference happening between two waves, what are they doing to each other?

Back 27

Annulling each other.

Front 28

Write out the derivation for path difference.

Back 28

Front 29

Since path difference = dsinθ and dsin θ = mλ, what equation represents the path difference of an 'm'th minimum?

Back 29

dsin θ = (m-0.5) λ

(Where 'm' is equal to the number minimum. e.g. "Find the 3rd minimum of the interference pattern" m=3 in this case).

Front 30

Since path difference = dsin θ and dsin θ = m λ, what equation represents the path difference of an 'm'th maximum?

Back 30

dsin θ = m λ

(Where 'm' is equal to the number maximum. e.g. "Find the 3rd maximum of the interference pattern" m=3 in this case).

Front 31

Write out the derivation of fringe separation.

Back 31

Front 32

Write out the derivation of path difference between adjacent waves.

Back 32

Front 33

Define the work function of a metal surface.

Back 33

The work function of a metal surface is the minimum energy required to remove an electron from the metal.

Front 34

What are the four characteristics/properties of the photoelectric effect?

Back 34

1) The threshold frequency. This represents the minimum frequency for emission to occur.

2) If radiation is above the threshold frequency, the emission of electrons is instantaneous, regardless of how weak the intensity of the radiation.

3) The current (the number of electrons released per unit time) is independent of frequency and directly proportional to the intensity.

4) The maximum kinetic energy of emitted electrons is linearly dependent on the frequency of radiation.

Front 35

What is the slope of a kinetic energy v. frequency graph given as?

Back 35

6.63x10^-34 Js (also known as Planck's constant or 'h').

Front 36

What are Einstein's three assumptions about the photoelectric effect?

Back 36

1) Light is not emitted as a continuous wave but rather as discrete bundles of energy known as photons.

2) The intensity of radiation is proportional to the number of photons crossing a unit of area per unit time.

3) When a photon collides with an electron, it may transfer its energy. If any energy is transferred, all of it must transfer. (A photon may keep all or no energy).

Front 37

What is equation used to find the maximum kinetic energy of an emitted electron?

Back 37

Kmax = hf - W

Front 38

What is the y-intercept of a kinetic energy v. frequency graph given as?

Back 38

The work function.

Front 39

What causes characteristic X-rays?

Back 39

A voltage increase which is high enough in the X-ray tube will cause high intensity peaks. (This all depends on the material used, hence why it is called characteristic).

Front 40

What is a general rule to do with the duality of light?

Back 40

Light is generally considered a wave when referring to its propagation, transmission, refraction, reflection or diffraction.

Light is generally considered a particle when referring to its interactions with matter. E.g. emission of electrons from a metal surface.

Front 41

What three factors must be considered when taking an X-ray photo?

Back 41

1) The attenuation of the X-ray.

2) The penetrating power of the X-ray.

3) The exposure time of the X-ray.

Front 42

What is meant by the attenuation of an X-ray?

Back 42

The degree in which X-radiation is absorbed by the object. In humans, the density, thickness and atomic number of the elements of tissue affect the absorption.

Front 43

What is meant by the de Broglie wavelength?

Back 43

The wavelength of a particle. (e.g. a proton acting as a particle or the wavelength of a person running).

Front 44

What was the purpose of the Davisson-Germer experiment?

Back 44

To determine that particles can indeed behave like waves. A beam of low energy electrons were fired at a nickel crystal and the evenly spaced atoms of the crystal reflected the electrons, representing wave-like properties since the crystal acts as a diffraction grating for the electron matter waves.

Front 45

X-rays are emitted with a _____________ range of frequencies, ranging up to a maximum.

Back 45

Continuous.

Front 46

What relationships exist in X-rays? (e.g. frequencies, voltages etc).

Back 46

- As the voltage of the tube increases, so does the maximum frequency and intensity of emitted X-rays.

- Maximum frequency is directly proportional to the voltage applied across the tube.

Front 47

What is an X-ray? (Hint: 4 points to mention).

Back 47

1) High frequency E-M radiation

2) Produced when electrons are accelerated to high speeds by a high potential difference and collide with a metal.

3) Voltages required between 20,000 - 200,000 V.

4) Most energy is converted to heat when electrons collide with the anode. (98+%). Some energy is retained and is emitted as X-rays. Depending on how close they approach (random distances means random accelerations), lose some or all energy. This energy is transformed to light and has various energies and hence, various frequencies.

Front 48

What preparations are made to an X-ray tube to create X-rays? (Hint: 3 points to mention).

Back 48

1) The cathode is heated to give electrons energy, allowing them to leave the cathode more easily.

2) Anode must be a good conductor of heat. (Often copper).

3) Cooling fins are used to pull heat away from anode since otherwise the anode may melt over extended use.

Front 49

By conservation of energy...

Back 49

hfmax = eV

Front 50

When can an electron microscope be used?

Back 50

When the particle has a de Broglie wavelength.

Front 51

What does the intensity distribution graph look like in double slit experiment?

Back 51

Front 52

What does the intensity distribution graph look like in a diffraction grating?

Back 52