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Edexcel IGCSE Physics > Section 3 - Waves > Flashcards

Section 3 - Waves Flashcards

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1
Q

What are the differences between longitudinal and transverse waves?

A

In longitudinal waves, the vibrations are along the same direction as the wave transfers energy

In transverse waves, the vibrations are at 90* to the direction energy is transferred by the wave

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2
Q

How can we show the differences between longitudinal and transverse waves?

A

We can create transverse waves on a slinky by wiggling it up and down.

We can create longitudinal waves on a slinky by compressing it

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3
Q

Define amplitude

A

It is the height of the wave (from rest to crest(

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4
Q

Define frequency

A

It is how many complete waves there are per second. (Hz)

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5
Q

Define wavelength

A

It is the distance from one peak to the next

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6
Q

Define period

A

It is the time it takes (in s) for one complete wave to pass a point

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7
Q

What properties of wave make it useful?

A

Waves transfer energy and information without transferring matter

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8
Q

what is the equation for WAVE SPEED?

A

Wave Speed = Frequency x Wavelength

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9
Q

What is the equation for FREQUENCY?

A

Frequency = 1 / Time Period

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10
Q

What happens when a wave passes an edge? Explain why this is so. *

A

The wave diffracts when it passes an edge or through gaps

The narrower the gap, or longer the wavelength, the more the wave spreads out

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11
Q

What are the seven types of electromagnetic (EM) waves?

A

In increasing frequency and decreasing wavelength order:

  1. Radio Waves
  2. Micro-Waves
  3. Infra-Red
  4. Visible Light
  5. Ultra-Violet
  6. X-Rays
  7. Gamma Rays
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12
Q

Which electromagnetic wave travels the fastest in free space?

A

They all travel at the same speed

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13
Q

Which colour has the longest wavelength and lowest frequency and which colour has the shortest wavelength and highest frequency?

A

Longest Wavelength and Lowest Frequency - Red

Shortest Wavelength and Highest Frequency - Violet

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14
Q

What are radio waves used for?

A

Broadcasting and communications

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15
Q

What are microwaves used for

A

Cooking and satellite transmissions

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16
Q

What is infrared used for?

A

Heaters and night vision equipment

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17
Q

What is visible light used for?

A

Optical fibres and photography

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18
Q

what is ultraviolet used for?

A

Fluorescent lamp

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19
Q

What are x-rays used for?

A

Observing the internal structure of objects and materials and medical applications

20
Q

What are gamma rays used for?

A

Sterilising food and medical equipment

21
Q

What happens if an individual is exposed to too much microwaves and how can an individual be protected from it?

A

Microwaves can increase vibrations of molecules, which can cause internal heating.

Protection - microwave ovens are shielded so they can’t escape

22
Q

What happens if an individual is exposed to too much infrared and how can an individual be protected from it?

A

Infrared waves can increase vibrations of surface molecules, which can cause skin burns.

Protection - use insulating materials to reduce the amount of IR reaching your skin

23
Q

What happens if an individual is exposed to too much ultraviolet and how can an individual be protected from it?

A

Damage to surface cells and blindness as it is ‘ionising’, so it can knock electrons off atoms and cause cell mutations.

Protection - wear suncream with UV filters and stay out of strong sunlight

24
Q

What happens if an individual is exposed to too much gamma rays and how can an individual be protected from it?

A

Gamma rays are ionising and can penetrate the body, so they can cause cell mutation or destruction, which leads to tissue damage and cancer

Protection - keep sources of gamma rays in led-lined boxes and keep exposure time to a minimum

25
Q

What happens when a light wave is reflected?

A

Light hitting the reflective surface will ‘bounce’ back from the surface at the same angle the hit the surface

26
Q

What happens when a light is refracted?

A

Light waves change speed when they go through objects with different densities, which causes them to change direction. When they return to the original density, they will continue in the original direction

27
Q

What happens when a light is diffracted? *

A

When light meets a barrier, it will carry on through the gap and spread out in the area beyond

28
Q

What is the law of reflection?

A

The angle of incidence equals the angle of reflection

29
Q

Describe an experiment to investigate the refraction of light?

A
  • Shine a light ray at an angle into the block.
  • Trace the incident and emergent rays onto the piece of paper and remove the block.
  • You can now draw in the refracted ray by joining the ends- of the two other rays

You will notice that when light passes from air into a denser medium, it bends towards the normal as it slows down

30
Q

What is the equation for the REFRACTIVE INDEX?

A

Refractive Index = Sin (Incidence) / Sin (Refraction)

31
Q

How do you transmit information along optical fibres and in prisms?

A

Beyond the critical angle, light will be reflected back into the medium they came form at the same angle. In this way, they are trapped in the medium.

By reflecting light past its critical angle, you can make it travel through a medium to send information, which is done in optical fibres.

32
Q

What is the critical angle?

A

The critical angle is a certain angle of incidence in which the light will be refracted at 90*

If the light ray is shone at a greater angle than angle c, the light will be reflected back into the medium it is in. This is called total internal reflection

33
Q

What is the equation for the CRITICAL ANGLE?

A

Sin (Critical Angle) = 1 / Refractive Index

34
Q

What is the difference between analogue and digital signals? *

A

Analogue - it can take up any value within a certain range. The amplitude and frequency can vary continuously

Digital - it can only take two values (on/off or 1/0)

35
Q

What are the advantages of using digital signals rather than analogue signals? *

A

When analogue signals get amplified, the noise is amplified too and the signal loses quality. When digital signals get amplified, the noise is ignored, so it remains high quality.

36
Q

Describe how digital signals can carry more information *

A

Many ways:

  • Multiplexing (as there is less interference) means more information can be transmit along the same channel
  • Increasing bandwidth (measure of how much info can be sent) can be increased
  • Increase the frequency, so more pulses are sent per second
37
Q

What kind of waves are sound waves?

A

They are longitudinal

38
Q

How can sound waves be reflected?

A

They will be reflected by hard flat surface

39
Q

How can sound waves be refracted?

A

If they enter a different media. As they enter denser material, they speed up.

40
Q

How can sound waves be diffracted? *

A

They can be diffracted through gaps and around obstacles.

41
Q

What is the frequency range for human hearing?

A

20 Hz - 20,000 Hz

42
Q

Describe an experiment to measure the speed of sound in air

A

Measure the distance between two places.
Have a sound made in one place.
As soon as you see the signal that the sound has been made, start the stop watch. As soon as you hear the sound stop the stopwatch.

speed = distance / time

43
Q

How can an oscilloscope and microphone be used to display a sound wave? *

A

A microphone is plugged into the oscilloscope and the microphone converts the sound waves to electrical signals. The oscilloscope displays the microphone signal as a trace on a screen.

44
Q

Describe an experiment using an oscilloscope to determine the frequency of a sound wave *

A

Adjust the time division setting until the display shows at least 1 complete cycle of a wave.

Read off the period - the time it takes for one complete cycle.

Frequency = 1 / Period

45
Q

How is the pitch of a sound determined? *

A

The pitch of a sound is determined by the frequency of the wave

46
Q

How is the loudness of a sound determined? *

A

The greater the amplitude of a wave or vibration, the more energy it carries.

In sound, this means that it will be louder.

Edexcel IGCSE Physics (7 decks)

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