Waves

Question 1

Definition of Amplitude

Answer 1

Maximum displacement from the equilibrium

Question 2

Definition of Wavelength

Answer 2

The shortest distance between 2 adjacent points that are in phase

Question 3

Definition of Frequency

Answer 3

The number of oscillations per second, number of waves passing a point in 1 second.

Question 4

Definition of Period

Answer 4

Time for a wave for one complete oscillation

Question 5

What is the speed of light in air?

Answer 5

3x10^8 m/s^-1

Question 6

Describe a longitudinal wave and an example

Answer 6

When the oscillations are parallel to the direction of travel. Sound waves

Question 7

What is a wavefront?

Answer 7

A line representing a series of equivalent points on the waves.

Question 8

Describe transverse waves and an example.

Answer 8

When the oscillations are at right angles to the direction of wave travel. electro magnetic field

Question 9

When are waves in phase?

Answer 9

When crests meet crests and troughs meet troughs

Question 10

When are wave in antphase

Answer 10

When crests meet troughs and troughs meet crests

Question 11

When does superposition take place and describe it.

Answer 11

When two or more waves arrive at the same place at the same time. If they are in phase then the superposition is constructive and produces a larger amplitude. and vise versa. (destructive)

Question 12

When are waves coherent?

Answer 12

When two sets of waves have the same frequency and a constant phase difference

Question 13

When do standing waves occur and example

Answer 13

Superposition of two progressive waves of equal frequency and amplitude moving in opposite directions. Two speakers facing each other.

Question 14

Describe nodes and antinodes

Answer 14

The points of zero amplitude within a standing wave are nodes, and the maximum displacement points are antinodes.

Question 15

Identify different regions of electromagnetic spectrum and their uses

Answer 15

RADIO WAVES:Tv, radio transmissions.
MICRO WAVES:Mobile phone links
INFRARED: Alarm systems, warm bodies emit infrared waves that are detected
VISIBLE LIGHT
ULTRAVIOLET: disco wrist stamps
X-RAYS: Penetrating, image objects in a suitcase
GAMMA RAYS: Hospitals to sterilize equipment

Question 16

What happens as you go down the electro spectrum and upwards?

Answer 16

Upwards towards radio waves is increase in wavelength and downwards towards gamma rays is increase in frequency.

Question 17

The colors in order

Answer 17

ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, Violet.

Question 18

Describe Pulse-echo technique and example

Answer 18

Waves reflect from a boundary between two media, greater density between two materials the stronger the reflection. A pulse is required so that the time interval between the incident pulse and the reflected pulse can be measured. Medical/ physio uses.

Question 19

What is the doppler effect? and example

Answer 19

Waves are emitted from a moving sound or detected by a moving receiver, the detected frequency’s differ from the emitted req. THE SHIFT IN FREQ IS POPORTIONAL TO V OF MOTION.

Used in medicine for ultrasound

Question 20

What is refraction?

Answer 20

When waves meet a boundary between two materials, some of the wave is transmitted and reflected. Transmitted waves changes speed and may change direction.

Question 21

What is total internal reflection ?

Answer 21

Occurs when a wave passes from a greater density to less.

Angle of incidence within the material is greater than the critical angle.

Question 22

How do you measure refractive index?

Answer 22

sini/sinr or v1/v2

Question 23

Situations that require accurate determination of refractive index?

Answer 23

Fishing, use same ref.in as water so fish don’t see the line and just the bait.

Question 24

What is meant by plane polarized light? And what type of waves cannot be polarised and why

Answer 24

The variations in electric field take place only in one plane. Longitudinal waves such as sound cannot be polarised

Question 25

How do you measure the rotation of the plane of polarisation?

Answer 25

Optically active substances such as sugar solutions rotate the plane of polarisation by an amount proportional to their concentration and the depth of liquid through which light travels thus this can be used to measure the concentration of sugar solutions.

Question 26

What is diffraction and relation to width of gap?

Answer 26

The spreading of wavefronts as a wave passes through a gap or around an object. The amount of diffraction is greatest when the wavelength is similar to the size of the gap or object.

Question 27

Explain how diffraction experiments provide evidence for the wave nature of electrons

Answer 27

When a beam of electrons is directed at a crystal, a pattern can be observed. The electron beam must have diffracted through the layers of atoms in the crystal suggesting that electrons behave like waves. The wavelength of the electron beam must be similar to the distance between the layers of atoms in the crystal.

Question 28

Discuss how scientific ideas may change over time, our ideas on the particle/wave nature of electons

Answer 28

x

Question 29

How is ultrasound used for fetus's

Answer 29

Reflected pulses of ultrasound are used to determine where the boundaries are between different tissues.

Question 30

What is meant by resolution and how can you improve it.

Answer 30

The smallest level of detail that can be seen, can be improved by reducing the wavelength of the sound used.

Question 31

How to measure critical angle?

Answer 31

RI=1/SinC

Question 32

What happens when light passes through a polarising filter? And if they are crossed?

Answer 32

The light becomes polarised and if two polarising filters are aranged so that they are at right angles to each other, then they will completely absorb unpolarised light

Question 33

How can X-rays be used to show the arrangement of atoms within solid materials?

Answer 33

The layers of atoms solid materials can act as a series of gaps or slits. The X-rays first diffract as they pass through the gap. Superposition of X-rays from different layers will then produce an interference pattern. If there is a regular pattern then the atoms in the solid are structured.

Question 33

What type of waves are the ones from the electromagnetic spectrum?

Answer 33

Transverse