Waves

Question 1

In phase

Answer 1

Waves doing the same thing at the same time

Same phase angle, constructive interference

Question 2

In antiphase

Answer 2

Phase angle of pie/180deg, destructive interference

Question 3

Out of phase

Answer 3

Phase angle of x, interference

Question 4

Antinode

Answer 4

Max amplitude

Question 5

Node

Answer 5

No amplitude

Question 6

How are standing waves formed?

Answer 6

When an incident wave reflects off * a surface. The reflected wave superposes with the incident wave. Nodes are formed when the amplitude is zero. Antinodes are formed where the amplitude is at a maximum.

• or- the open end of the tube due to the pressure change

Question 7

Refractive index

Answer 7

The amount light slows down when it interacts with electrons in a material.

n= cmaterial1/ cmaterial2

Question 8

Snells law

Answer 8

n1sinx1=n2sinx2

Question 9

Reducing uncertainty when measuring waves

Answer 9

Use:
Laser
Smaller beam
larger protractor

Question 10

Double slit:
Frequency increases

Answer 10

Spacing between maxima decreases

Question 11

Double slit:
Spacing between sources increases

Answer 11

Maxima spacing decreases

Question 12

Double slit:
distance away from sources increases

Answer 12

Maxima spacing increases

Question 13

Path difference

Answer 13

Difference in distance travelled by waves arriving from two sources

Question 14

Diffraction- Huygens principle

Answer 14

Each point on a wave front maybe considered as a secondary source. They all produce wavelets. (Circular, same speed, frequency, wavelength)

Question 15

Monochromatic

Answer 15

Single wavelength

Question 16

Coherent

Answer 16

Sources have a fixed phase relationship

Question 17

Youngs double slit equations

Answer 17

Wavelength = xd/ l
X- fringe spacing, d- slit spacing, l- screen distance

n x wavelength = d sinO

Question 18

Wave particle duality

Answer 18

Einstein reasoned that light could be thought of as a continuous stream of photons

Question 19

Photoelectric effect

Answer 19

There is an energy cost to remove an electron from an atom, this is called the work function.
KE= hf - O
O- work function

Question 20

Electron volts

Answer 20

The energy needed to move one electron through one volt of pd.

1eV=1.6x10^-9 J

Question 21

Absorption and emission

Answer 21

Electron absorbs energy (arrow goes up).
Electron drops back down an energy level and emits a photon (arrow goes down)

Question 22

Many paths

Answer 22

A photon is emitted by a source and is detected at a certain place and time.

The longer the path the earlier it had to have been emitted

Question 23

Probability of a photon arriving

Answer 23

-The intensity is proportional to the probability of a photon arriving.
(Intensity is the rate at which energy arrives at a point on a screen)
- probability is given by the square of the length of phasor

Question 24

Electron diffraction

Answer 24

• two physicists showed that electrons formed a diffraction pattern when they passed through a thin layer of graphite crystal.
• if brightness turned very low, we can see individual electrons (with a sensitive screen). Evidence for particle theory.
• as more electrons hit the screen, a diffraction pattern appears. Evidence for wave theory

Question 25

Electron microscopes and quantum nature of electrons

Answer 25

- an electron explores every path from the transmitter to the receiver. - for every wavelength it travels, its phasor spins once. - adding all the phasors together gives a resultant phasor. - probability of detecting an electron is proportional to the square of the phasor amplitude.