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waves Flashcards

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1
Q

What is Interference?

A

Modification of intensity or amplitude when two or more waves are superimposed.

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2
Q

Define Constructive interference.

A

Interference where the resultant amplitude is the sum of the amplitudes due to two waves.

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3
Q

Define Destructive interference.

A

Interference where the resultant amplitude is equal to the difference of two amplitudes.

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4
Q

What does the Principle of Superposition state?

A

Resultant displacement of a particle is the algebraic sum of displacements due to individual waves.

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5
Q

What is the formula for resultant displacement in superposition?

A

y = y1 ± y2

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6
Q

What is the effect on amplitude when y1 and y2 are in the same direction?

A

The amplitude is summed.

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7
Q

What happens when y1 and y2 are in opposite directions?

A

The amplitude is subtracted.

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8
Q

What is the path difference in thin films?

A

Path difference = μ(AC + CD) - AB

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9
Q

What is the condition for maximum intensity in thin films?

A

Path difference = nλ

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10
Q

What is the path difference when light reflects at a rarer-denser interface?

A

Extra phase difference of π or path difference of λ/2.

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11
Q

What is the condition for minimum intensity in thin films?

A

Path difference = (2n + 1)λ/2

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12
Q

What are Newton’s rings?

A

Interference pattern formed by alternate bright and dark concentric circular rings.

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13
Q

What type of light is used in the Newton’s ring experiment?

A

Monochromatic light.

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14
Q

What is the formula for the diameter of dark rings in Newton’s ring experiment?

A

D² = 4Rnλ/n

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15
Q

What is required to obtain stationary interference fringes?

A

Two coherent sources emitting continuous waves of the same wavelength.

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16
Q

What causes colors in thin films?

A

Path difference changes with thickness and wavelength of light.

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17
Q

Define diffraction.

A

Bending of light when it encounters obstacles or small apertures comparable to its wavelength.

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18
Q

List differences between Interference and Diffraction.

A
  • Interference is due to two coherent sources
  • Diffraction is due to secondary wavelets from the same wave front
  • Interference fringes may vary in width
  • Diffraction fringes are not of uniform width
  • Minimum intensity points in interference are perfectly dark
  • Minimum intensity points in diffraction are not perfectly dark
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19
Q

What are the two types of diffraction?

A
  • Fresnel Diffraction
  • Fraunhofer Diffraction
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20
Q

What is the primary difference between Fresnel and Fraunhofer diffraction?

A

Fresnel uses point sources or narrow slits; Fraunhofer uses extended sources at infinite distance.

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21
Q

What is the path difference for maximum intensity in Fraunhofer diffraction?

A

Condition: sin(α) = 0

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22
Q

What is the formula for intensity in Fraunhofer diffraction?

A

I = R² = A² (sin(α)/α)²

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23
Q

When does maximum intensity occur in Fraunhofer diffraction?

A

When α = 0.

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24
Q

What is the principal maximum in Fraunhofer diffraction?

A

Maximum intensity at θ = 0.

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25
What happens when sin(α) = 0 in the context of diffraction?
Minimum intensity occurs.
26
When is the value of R maximum?
When α = 0, i.e., θ = 0 ## Footnote This condition leads to maximum intensity.
27
What is the formula for maximum intensity I?
I = R² = A² ## Footnote This occurs at θ = 0, known as principal maximum.
28
What are the positions of minimum intensity?
When sin α = 0, α = ±mπ ## Footnote This results in minimum intensity positions.
29
How can secondary maxima be described?
Weak secondary maxima occur between equally spaced minima ## Footnote Found in addition to principal maxima.
30
What is the relationship between sin α and positions of maximum?
α cos α = sin α ## Footnote This equation helps find positions of maxima.
31
What does the intensity distribution graph represent?
Intensity distribution in diffraction patterns ## Footnote Shows the variation of intensity with angle.
32
What is the condition for principal maxima in a grating?
(e + d) sin θ = nλ ## Footnote Where n is an integer representing the order of maxima.
33
What is the effect of increasing the number of slits in a grating?
The intensity of secondary maxima decreases ## Footnote As N increases, the distribution of intensity changes.
34
What is the definition of dispersive power of a grating?
The rate of variation of angle of diffraction with wavelength ## Footnote Expressed as dθ/dλ.
35
What is the resolving power of a grating?
The capacity to form separate diffraction maxima of two close wavelengths ## Footnote Defined based on Rayleigh's criterion.
36
What is the significance of Rayleigh’s criterion?
Two wavelengths are resolved when the principal maximum of one falls on the first minimum of the other ## Footnote This ensures distinguishability of closely spaced wavelengths.
37
What happens to the angle of diffraction for different wavelengths?
Longer wavelengths have greater angles of diffraction ## Footnote This leads to the separation of spectral colors.
38
What is the general condition for maxima in diffraction grating?
(e + d) sin θ = nλ ## Footnote This condition describes the angle at which maxima occur.
39
What occurs at minimum intensity positions in grating?
sin Nβ = 0, but sin β ≠ 0 ## Footnote Results in values for m excluding multiples of N.
40
What are the characteristics of grating spectra?
* Symmetrical spectral lines on both sides of zero order * Spectral lines are sharp and straight * Colors range from violet to red * Most intensity is in zero order ## Footnote These properties define the appearance and quality of the spectrum produced.
41
Fill in the blank: The intensity at any point on the screen is given by the product of __________.
Diffraction term and interference term ## Footnote Reflects the combination of effects in a diffraction pattern.
42
What is the expression for Resolving power of a grating based on Rayleigh’s criterion?
Resolving power is derived from Rayleigh’s criterion.
43
What is the action of a plane transmission grating in producing a diffraction spectrum?
It disperses light into its constituent wavelengths.
44
Can a grating with 500 lines/cm give a spectrum in 4th order for light of wavelength 5890 Å?
No, it cannot.
45
What is polarization?
It is the process of converting ordinary light into polarized light.
46
What defines a polarized wave?
A wave that is unsymmetrical about the direction of propagation.
47
What is polarized light?
Light that has acquired the property of one-sidedness.
48
What happens when ordinary light passes through a pair of tourmaline crystal plates with planes parallel?
Maximum intensity is obtained.
49
What happens when the planes of tourmaline crystal plates are perpendicular to each other?
The intensity is zero.
50
What are the three types of polarized light?
* Plane polarized light * Circularly polarized light * Elliptically polarized light
51
Define plane polarized light.
Light where vibrations are confined along a single direction.
52
Describe circularly polarized light.
Vibrations rotate in a circle, resulting in right or left circularly polarized light.
53
What characterizes elliptically polarized light?
Vibrations follow an ellipse, and the amplitude vector varies periodically.
54
What is unpolarized light?
Light with vibrations both parallel and perpendicular to the plane of the paper.
55
What is partially polarized light?
Linearly polarized light containing a small additional component of unpolarized light.
56
What is Brewster's Law?
The tangent of the angle of polarization (P) equals the refractive index of the material.
57
What is the significance of the angle between reflected and refracted rays according to Brewster’s law?
They are perpendicular to each other.
58
What is a pile of plates in the context of polarization?
An arrangement where repeated reflection at polarizing angle produces purely plane polarized light.
59
What is calcite?
A transparent colorless crystal, chemically hydrated calcium carbonate.
60
What is birefringence?
The phenomenon where a beam of ordinary unpolarized light splits into two refracted rays.
61
What are ordinary and extraordinary rays?
* Ordinary ray: obeys ordinary laws of refraction * Extraordinary ray: does not obey general laws of refraction
62
What is a Nicol prism?
A device that eliminates the ordinary beam using total internal reflection.
63
How does a Nicol prism function as both a polarizer and analyzer?
The first Nicol produces polarized light, while the second analyzes it.
64
What is a half wave plate?
A crystal that introduces a path difference of λ/2.
65
What is a quarter wave plate?
A crystal that introduces a path difference of λ/4.
66
What is the condition for a half wave plate?
(μe - μo)t = λ/2.
67
What is the condition for a quarter wave plate?
(μe - μo)t = λ/4.

applied physics (1 decks)

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