9. Wave phenomena

Question 1

Define amplitude in SHM

Answer 1

The maximum magnitude of displacement from the equilibrium position

Question 2

Define angular frequency (omega)

Answer 2

Rate of angular displacement

Question 3

Define SHM

Answer 3

An oscillatory motion of a particle whose acceleration is directly proportional to its displacement from the equilibrium position and this acceleration is always directed towards that position

Question 4

Define phase difference

Answer 4

The difference in phase angle between the 2 oscillations which have the same frequency/velocity

Question 5

When is KE of a particle in SHM maximum?

Answer 5

At equilibrium position

Question 6

When is PE of a particle in SHM maximum?

Answer 6

At the amplitudes

Question 7

Visualise the graph of total energy against displacement

Answer 7

KE - sin

PE - cos

Question 8

Visualise the graph of energy against time

Answer 8

Depends on where x starts at when t=0

Question 9

If a particle in SHM moves to the right, where is the acceleration towards?

Answer 9

The left. Vice versa.

Question 10

In circular motion, where does v point towards?

Answer 10

Tangent of the circle

Question 11

In circular motion, where does ‘a’ point towards?

Answer 11

Center of the circle

Question 12

What is the intensity profile of diffraction by a single slit like?

Answer 12

Highest peak in the middle, decreases on both sides after the central maxima.

Question 13

What happens when we increase the slit width?

Answer 13

Intensity increases since more light gets through, but central maxima becomes narrower

Question 14

What does the area under the graph for the intensity profile represent?
What happens to the area under the graph as the slit width increases?

Answer 14

It represents total energy.

The area under the graph also increases since more light now passes through the slit

Question 15

What is the modulation effect?

Answer 15

The intensities of the maxima of the double slit pattern is enveloped and bounded by the intensity distribution of the single slit pattern

Question 16

What is diffraction grating?

Answer 16

An optical component that consists of a large number of parallel equally spaced narrow slits

Question 17

What happens as the number of slits increase?

Answer 17

The bright peaks grow narrower and more intense

Question 18

Why is the maxima narrower when there are more slits?

Answer 18

More rays coming in at different angles does not allow for partial constructive interference outside of the optimal angle that gives the maxima. (must be exact)

Question 19

What is optical path length?

Answer 19

The product of the geometric length of the path followed by light though a given system, and the index of refraction of the medium through which it propagates
L0 = nL

Question 20

What are the 4 different variations for the 3 mediums for thin film interference?

Answer 20

1. Less –> More –> Less
2. More –> Less –> More
3. Less –> More –> Even more
4. Even more –> More –> Less

Question 21

For the 2 variations with
1. 180 deg phase change
2. No phase change,
what are the equations for constructive & destructive interference?

Answer 21

Constructive: 2dn = (m + 1/2)lamda
Destructive: 2dn = m*lambda

Question 22

What factors affect the interference of the rays during thin film interference?

Answer 22

Wavelength
Film thickness
Refractive indices

Question 23

What happens during thin film interference?

Answer 23

When light encounters an interface & a portion of it gets reflected, and the rest pass into the incident medium and get refracted
Basically a combination of the reflected and refracted rays

Question 24

When do you get multicoloured fringes in thin film interference?

Answer 24

When white light falls onto a thin film & the different wavelengths form fringes at different angles

Question 25

Definition of resolution

Answer 25

Minimum distance between distinguishable objects in an image

Or: Minimum resolvable distance

Question 26

What is the Rayleigh criterion?

Answer 26

Two sources are just resolvable when the first minimum of the diffraction pattern of one of the sources falls on the central maximum of the diffraction pattern of the other source

Question 27

What is the difference in the equation for Rayleigh’s criterion for a circular aperture and a single-slit aperture?

Answer 27

For circular aperture:
theta = 1.22lambda/b
Single-slit aperture:
theta = lambda/b

Question 28

When is the diffraction pattern unresolved?

Answer 28

When alpha < theta

Question 29

What is an adaptation of radio telescopes for higher resolution?

Answer 29

Increase b (diameter), so that theta decreases

Question 30

What is an adaptation of CDs/DVDs for higher resolution?

Answer 30

Reduce the wavelength of light so that theta is decreased

Question 31

What does resolvance mean?

Answer 31

The ratio of the wavelength of the light to the smallest difference in wavelength that can be resolved by the grating
Or: The ability of a diffraction grating to resolve these wavelengths

Question 32

Definition of Doppler Effect

Answer 32

The change in measured frequency of a waves that results from the relative motion of a source and/or an observer relative to the medium in which the wave is propagated.

Question 33

What can you observe about a wave when a source is moving towards an observer?

Answer 33

Higher frequency, shorter wavelength

Question 34

What can you observe about a wave when an observer is moving with respect to a stationary source?

Answer 34

Higher wave speed, higher frequency

Question 35

What is the effect of wind blowing from the direction of a stationary source towards a stationary observer?

Answer 35

Higher wave speed, higher wavelength