4.3 Wave Characteristics

Question 1

Sound Intensity (I)

Answer 1

The amount of energy that a sound wave brings to a unit area every second.

Question 2

Sound Intensity Proportionality

Answer 2

I ∝ A^2 for all waves

Question 3

Inverse Square Law of Radiation (ISLR)

Answer 3

As the distance of an observer from a point of source of light increases, the power received by the observer will decrease as the energy spreads out over a larger area.

Question 4

Solar Constant Value (S)

Answer 4

1.36 x 10^3 in Wm^-2

Question 5

(ISLR) effect on Intensity

Answer 5

I = P/4πr^2

Question 6

Ray

Answer 6

The path taken by the wave energy as it travels outwards from the source.

Question 7

Wavefront

Answer 7

A surface joining neighbouring points where the oscillations are in phase with one another.

Question 8

Interference of Waves

Answer 8

Two waves which meet interfere with one another and the resulting wave can be worked out through the principle of superposition.

Question 9

Types of Interference of Waves

Answer 9

If the waves have the same amplitude and the same frequency then the interference at a particular point can be constructive or destructive.

Question 10

Constructive Inference

Answer 10

Takes place when two waves are in phase.

Question 11

Destructive Inference

Answer 11

Takes place when two waves are exactly out of phase (180 degrees).

Question 12

Path Difference Constructive

Answer 12

𝑛𝜆

Question 13

Path Difference Destructive

Answer 13

(𝑛+1/2)𝜆

Question 14

Superposition of Wave Pulses

Answer 14

Occurs when wave pulses meet. At any instant in time, the net displacement that results from different waves meeting at the same point in space is just the vector sum of the displacements that would have been produced by each individual wave.

Question 15

Plane of Vibration

Answer 15

The plane that contains the electric field and the direction of propagation.

Question 16

Unpolarized Light vs Polarized Light

Answer 16

If unpolarized light, the plane of vibration varies randomly whereas plane-polarized light has a fixed plane of vibration.

Question 17

Circularly Polarized

Answer 17

When the plane of polarization rotates uniformly.

Question 18

Polarizer

Answer 18

Any device that produces plane-polarized light from an unpolarized beam.

Question 19

Analyser

Answer 19

A polarizer used to detect polarized light.

Question 20

Malus’s Law

Answer 20

When plane-polarized light is incident on an analyser, its preferred direction will allow a component of the light to be transmitted

Question 21

Malus’s Law - Transmitted Intensity

Answer 21

𝐼 = 𝐼0cos^2⁡𝜃
where
𝐼 is transmitted intensity of light in 𝑊 𝑚^(−2)
𝐼0 is the incident intensity of light in 𝑊 𝑚^(−2)
𝜃 is the angle between the plane of vibration and the analyser’s preferred direction

Question 22

Uses of Polarization

Answer 22

Polaroid Sunglasses

Liquid-Crystal Displays (LCDs)