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Physics Unit 2 > Waves > Flashcards

Waves Flashcards

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1
Q

Definition of Amplitude

A

Maximum displacement from the equilibrium

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2
Q

Definition of Wavelength

A

The shortest distance between 2 adjacent points that are in phase

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3
Q

Definition of Frequency

A

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

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4
Q

Definition of Period

A

Time for a wave for one complete oscillation

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5
Q

What is the speed of light in air?

A

3x10^8 m/s^-1

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6
Q

Describe a longitudinal wave and an example

A

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

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7
Q

What is a wavefront?

A

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

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8
Q

Describe transverse waves and an example.

A

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

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9
Q

When are waves in phase?

A

When crests meet crests and troughs meet troughs

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10
Q

When are wave in antphase

A

When crests meet troughs and troughs meet crests

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11
Q

When does superposition take place and describe it.

A

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)

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12
Q

When are waves coherent?

A

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

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13
Q

When do standing waves occur and example

A

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

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14
Q

Describe nodes and antinodes

A

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

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15
Q

Identify different regions of electromagnetic spectrum and their uses

A

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

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16
Q

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

A

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

17
Q

The colors in order

A

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

18
Q

Describe Pulse-echo technique and example

A

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.

19
Q

What is the doppler effect? and example

A

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

20
Q

What is refraction?

A

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

21
Q

What is total internal reflection ?

A

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

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

22
Q

How do you measure refractive index?

A

sini/sinr or v1/v2

23
Q

Situations that require accurate determination of refractive index?

A

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

24
Q

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

A

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

25
Q

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

A

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.

26
Q

What is diffraction and relation to width of gap?

A

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.

27
Q

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

A

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.

28
Q

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

A

x

29
Q

How is ultrasound used for fetus’s

A

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

30
Q

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

A

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

31
Q

How to measure critical angle?

A

RI=1/SinC

32
Q

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

A

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

33
Q

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

A

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.

33
Q

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

A

Transverse

Physics Unit 2 (3 decks)

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