12. Superposition

Question 1

What is the principle of superposition?

Answer 1

The principle of superposition states that when two waves meet at a point, the resultant displacement is equal to the vector sum of the individual displacements..

Question 2

What is interference?

Answer 2

Interference is when two waves overlap and interact to form a new wave pattern

Question 3

What are coherent sources?

Answer 3

Coherent sources are sources which provides waves os same frequency with a constant phase difference.

Question 4

What is coherence?

Answer 4

Coherence is used to indicate that two waves have constant phase difference.

Question 5

Two sources must be in phase to have constant phase difference?

Answer 5

False.

Question 6

What is path length?

Answer 6

Path length is the distance travelled from the source to a point.

Question 7

What is Path difference?

Answer 7

Path difference is the difference in path lengths when waves from two sources meet.

Question 8

What is Phase difference?

Answer 8

Phase difference is the measure of how much one wave is out of step with another. A phase difference of 1 cycle corresponds to 360° or 2∏ radians.

Question 9

What is the phase difference of waves that meet in phase?

Answer 9

2∏n, n=0, 1, 2, …

Question 10

What is the phase difference of waves that meet in antiphase?

Answer 10

(2n+1)∏, n= 0, 1, 2, …

Question 11

What is the formula for phase difference at a point?

Answer 11

phase difference = path difference/ wavelength x 2∏ ( phase difference between sources)

Question 12

What is constructive interference?

Answer 12

Constructive interference occurs when two waves from two or more sources arrive at a point in phase and reinforce each other. The amplitude of the resultant waves is the sum of amplitudes of the individual waves, giving rise to the maximum resultant amplitude.

Question 13

What is destructive inteference?

Answer 13

Destructive interference occurs when two waves from two or more sources arrive at a point exactly half-cycle out of phase. The amplitude of the resultant waves is the difference in amplitudes of the individual waves, giving rise to the minimum resultant amplitude.

Question 14

What is the 4 conditions for a steady and observable two-source interference?

Answer 14

1. Waves must overlap
2. Waves must be coherent
3. Waves must have approximately the same amplitude
4. transverse waves must either be polarized or unpolarized in the same plane.

Question 15

What is the formula of fringe separation ( double slit) ?

Answer 15

x = 𝛌D/ a
x is fringe separation (distance between bright fringes, distance between dark fringes)
𝛌 is wavelength of light
D is distance of double slit from screen
a is slit separation

Question 16

What is the formula for single slit diffraction?

Answer 16

sin𝛉 = 𝛌/b

𝛉 is the angle between the perpendicular to the slit and the first minimum
𝛌 is the wavelength
b is the width of the single slit

Question 17

what is the formula for the general condition for destructive interference for single slit diffraction?

Answer 17

b sin𝛉 = m𝛌

b is the width of single slit
𝛉 is the angle between the perpendicular to the slit and the first minimum
𝛌 is the wavelength
m = ±1, ±2, ±3, … ( order of minima)

Question 18

What is diffraction?

Answer 18

Diffraction is the spreading of waves when they pass through an opening or round an obstacle.
Diffraction effects are the greatest when the width of the opening is comparable with the wavelength of the waves.

Question 19

What is the Rayleigh criterion ( resolving images) ?

Answer 19

The rayleigh criterion is when the central maximum in the diffraction pattern of one images coincides with the first minimum of the diffraction pattern of the other image.

Question 20

What is resolving power?

Answer 20

The minimum separation of two objects that can be resolved by an optical instrument is called the limit of resolution. The smaller the limit of resolution, the greater the resolving power/ resolution of the instrument.

Question 21

How to improve resolution?

Answer 21

resolution improves when 𝛉 decreases.
1. use light of shorter wavelengths
2. larger aperture size

Question 22

What is the equation for diffraction grating?

Answer 22

d sin𝛉 = n𝛌
d is the separation between different slits ( number of slits per mm / mm)
n is the order of diffraction
𝛉 is the angle between the nth order beam and the normal beam
𝛌 is the wavelength of the beam

Question 23

What are stationary waves?

Answer 23

stationary waves are formed by two identical progressive waves travel in opposite directions towards each other and superpose, making it seem as though it does not propagate.

Question 24

What is a node?

Answer 24

A node is a point on a stationary wave where the amplitude of the vibration is zero or minimum.

Question 25

What is an antinode?

Answer 25

An antinode is a point on a stationary wave where the amplitude of the vibration is maximum.

Question 26

What are the properties of stationary waves?

Answer 26

1. stationary waves do not transfer energy through the medium
2. The nodes and antinodes are alternately situated.
3. All the particles in the medium, except those at the nodes follow simple harmonic motion