Waves

Question 1

phase difference

Answer 1

The phase difference between two waves is a measure of how much a point or a wave is in front or behind another

Question 2

And Q are two successive in phase points of tehy are separated by ?

Answer 2

2pi

Question 3

When are waves in anti-phase ?

Answer 3

When the crest of one wave aligns with the trough of another, they are in antiphase

Question 4

Simple harmonic motion (SHM) is defined as ?

Answer 4

The motion of an object whose acceleration is directly proportional but opposite in direction to the object’s displacement from a central equilibrium position

Question 5

The displacement-time graph for an object moving with SHM is a sinusoidal curve if ?

Answer 5

The object starts to oscillate from the equilibrium position.

Question 6

The displacement-time graph is a cosine curve if ?

Answer 6

The object starts to oscillate from the position of maximum displacement.

Question 7

Wavefront (2)

Answer 7

A wavefront is a line joining points moving in phase. It is normal ( or perpendicular) to teh direction of energy transfer in Teh wave

Question 8

Ray

Answer 8

A ray shows teh direction of energy transfer and is perpendicular or a wavefront

Question 9

Unpolarized light

Answer 9

A light wave that is vibrating in more than one plane is known as unpolarized light

Question 10

Polarized waves

Answer 10

When a transverse wave is polarised, its electric field is only allowed to oscillate in one fixed plane perpendicular to the direction of motion of the wave

Question 11

Unpolarized light (long definition)(3)

Answer 11

Unpolarized light consists of short bursts of electromagnetic waves emitted by many different atoms. The electric field directions of these bursts are perpendicular to the direction of wave travel, as in polarized light, but are distributed randomly about it.

Question 12

transmission axis of the material

Answer 12

The transmission axis of the material is the direction of polarization of the light that passes through the material.

Question 13

How does polarization work ?(3)

Answer 13

Light waves can be polarised by making them pass through a polarising filter called a polariser. The filter imposes its plane of polarisation on the incident light wave. A polariser with a vertical transmission axis only allows vertical oscillations to be transmitted through the filter (A)

Question 14

partial plane polarisation (3)

Answer 14

When unpolarised light reflects from a smooth non-metallic surface, partial plane polarisation always occurs
Reflected light is polarised in a plane parallel to the reflecting surface
This means if the surface is horizontal, a proportion of the reflected light will oscillate more in the horizontal plane than the vertical plane

Question 15

Polarized beams

Answer 15

When beams are polarised, the oscillations of the waves are made to oscillate only in one plane

Question 16

Reflected beams

Answer 16

When beams are reflected, they bounce back in the direction that they have come in by the same angle

Question 17

Plane polarisation

Answer 17

Plane polarisation is when the direction of the vibrations stays constant over time, and the vibrations are 100 % restricted in that direction

Question 18

Partial polarisation

Answer 18

Partial polarisation is when there is some restriction to the direction of the vibrations but not 100 %

Question 19

Intensity of Polarised Light(2)

Answer 19

The intensity of unpolarised light is reduced as a result of polarisation
If unpolarised light of intensity I0 passes through a polariser, the intensity of the transmitted polarised light falls by a half

Question 20

polariser

Answer 20

The first filter that the unpolarised light goes through is the polariser

Question 21

analyser

Answer 21

A second polarising filter placed after the first one is known as an analyser

Question 22

Why do ultrasound images have lower resolution (in comparison to EM imaging ) in medicine ?(2)

Answer 22

Ultrasound has a larger wavelength than x-rays; [1 mark]
Speed of ultrasound varies with different densities of tissues (Speed varying with greater ratios between tissues means that different tissues in the body (e.g. muscle in your leg compared to your arm) will transmit ultrasound in different waves.)

Question 23

Damping

Answer 23

The reduction in energy and amplitude of oscillations due to resistive forces on the oscillating system

Question 24

Light Damping

Answer 24

When oscillations are lightly damped, the amplitude does not decrease linearly
It decays exponentially with time

Question 25

Critical Damping

Answer 25

When a critically damped oscillator is displaced from the equilibrium, it will return to rest at its equilibrium position in the shortest possible time without oscillating

Question 26

Heavy Damping

Answer 26

When a heavily damped oscillator is displaced from the equilibrium, it will take a long time to return to its equilibrium position without oscillating

Question 27

Resistive force

Answer 27

Force that opposes the motion of the oscillator and causes damping

Question 28

When does maximum amplitude of the oscillations occur ?

Answer 28

The maximum amplitude of the oscillations occurs when the driving frequency is equal to the natural frequency of the oscillator

Question 29

free oscillation

Answer 29

An oscillation where there are only internal forces (and no external forces) acting and there is no energy input

Question 30

forced oscillations

Answer 30

Oscillations which are produced by a periodic external force

Question 31

natural frequency f0

Answer 31

The frequency of an oscillation when the oscillating system is allowed to oscillate freely

Question 32

driving frequency f

Answer 32

The frequency of the forced oscillations on a system is referred to as the driving frequency f