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IGCSE Physics > Waves > Flashcards

Waves Flashcards

1
Q

Describe a Transverse wave and give an example (2 marks)

A
  • In Transverse waves, vibrations are perpendicular (at 90) to direction the energy is transferred by the wave
  • Examples of transverse waves are light, electromagnetic waves, ripples on water
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2
Q

Describe a Longitudinal wave and give an example (2 marks)

A
  • In Longitudinal waves, vibrations are along the same direction as the wave transfers energy
  • Examples of transverse waves are sound and ultrasound
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3
Q

Describe the properties of Electromagnetic Waves

A
  • Electromagnetic waves are all Transverse waves
  • Electromagnetic waves all travel at the same speed through a vacuum
  • As you move from Radio Waves to Gamma Rays the FREQUENCE INCREASES and the WAVELENGTH DECREASES
  • For visible light, Red has the longest wavelength and Violet has the shortest wavelength
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4
Q

What are the uses of Radio Waves?

A
  • Radio waves are used mainly for communication
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5
Q

What are the uses of Microwaves?

A
  • Satellite communication
  • Mobile phone communication
  • Heating / cooking food
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6
Q

What are the uses of Infrared Radiation?

A
  • Infrared radiation is used to warm us and cook food
  • Infrared radiation is given out by all objects
  • Night vision equipment detects infrared radiation
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7
Q

What are the uses of Visible Light waves?

A
  • Communication using fibre optic cables
  • Pulses of light carry the data long distances
  • Visible light can also be used to see inside the human body without operating through scopes
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8
Q

What are the uses of Ultraviolet Waves?

A
  • Fluorescent lights use UV radiation to emit visible light
  • Fluorescent chemicals such as phosphor emit visible light by absorbing UV radiation
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9
Q

What are the uses of X-Ray Waves?

A
  • X-rays can be used to view internal structures of objects and materials including our bodies
  • X rays pass easily through flesh but not dense materials like bone or metal
  • X rays can cause mutations so patients and radiographers / doctors are protected by lead aprons, shields and exposure is kept to a minimum
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10
Q

What are the uses of Gamma Waves?

A
  • Gamma waves can sterilise medical equipment by killing microbes
  • Food can be kept sterilised by killing microbes meaning it stays fresher for longer
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11
Q

What does the term Total Internal Reflection mean? (2 marks)

A

When the angle of incidence exceeds the critical angle

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12
Q

What does the term refraction mean? (1 mark)

A

Waves change direction when they change medium

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13
Q

What does the term critical angle mean? (2 marks)

A

The angle of incidence above which gives total internal reflection

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14
Q

Give Two Uses of Total Internal Reflection (2 marks)

A
  • Fibre optic cables to transfer data
  • Binoculars
  • Periscope
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15
Q

Describe an investigation to measure the speed of sound in air using an oscilloscope (5 marks)

A
  • Connect a signal generator to a speaker and set at a known frequency
  • Connect two microphones to an oscilloscope
  • The two microphones will each show a wave on the oscilloscope
  • Start with the microphones next to the speaker and move one away until the two waves are aligned on the oscilloscope but one wavelength apart. The distance needs to be at least 1m
  • Measure the distance between the two microphones with a tape measure to find the wavelength
  • Repeat the experiment to get an average
  • Use the formula Speed = Frequency x wavelength to find the speed of the soundwaves. Use the wavelength you have measured, and the frequency is what the signal generator is set at
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16
Q

Describe an investigation to measure the speed of sound in air (5 marks)

A
  • Measure a distance of at least 100m using a trundle wheel / tape measure and have one person stand at either end
  • One person stands at either end. One person claps while the other person starts the stopwatch when they see the clap and stop it when they hear the clap
  • Repeat the experiment to get an average
  • Use Speed = Distance / Time to calculate the speed of sound using the distance you have measured and the timings from the stopwatch
17
Q

How would you use an oscilloscope to determine the frequency of a sound?

A
  • Adjust the oscilloscope to get a steady trace
  • Adjust the oscilloscope to get a minimum of one complete cycle on screen
  • Measure the number of squares for a number of completed cycles
  • Multiply the number of squares by the time base
  • Use f = 1/T
18
Q

What is the frequency of human hearing?

A

Human’s can hear frequencies between 20Hz and 20,000Hz

19
Q

How is the speed of sound affected by temperature?

A
  • The speed of sound decreases in lower temperatures
  • This is because the wavelength decreases with temperature
  • Speed = Frequency x Wavelength
20
Q

Why is the speed of sound faster in a liquid than air?

A
  • Sound travels by vibrations
  • Vibrations due to sound are passed on more effectively / faster in a liquid as the particles are closer together
21
Q

Explain Why the Sound Heard By Student A Has A Different Frequency To The Sound Emitted By The Buzzer? (5 marks)

A
  • Wavefronts are emitted by the buzzer at a constant frequency
  • Wavefronts arrive at Person A further apart than they were emitted
  • The distance between the wavefronts is the wavelength
  • Speed = Frequency x Wavelength
  • The speed of the waves is constant
  • As the speed of the waves is constant and wavelength has increased, frequency has decreased
  • A decrease in frequency is experienced as a decrease in pitch by Person A
  • This is the Doppler effect
22
Q

Answering the same question from Person B perspective (5 marks)

A
  • Wavefronts are emitted by the buzzer at a constant frequency
  • Wavefronts arrive at Person B closer together than they were emitted
  • The distance between the wavefronts is the wavelength
  • Speed = Frequency x Wavelength
  • The speed of the waves is constant
  • As the speed of the waves is constant and wavelength has decreased, frequency has increased
  • An increase in frequency is experienced as an increase in pitch by Person B
  • This is the Doppler Effect
23
Q

Answering the same question from Person B perspective (5 marks)

A
  • Wavefronts are emitted by the buzzer at a constant frequency
  • Wavefronts arrive at Person B closer together than they were emitted
  • The distance between the wavefronts is the wavelength
  • Speed = Frequency x Wavelength
  • The speed of the waves is constant
  • As the speed of the waves is constant and wavelength has decreased, frequency has increased
  • An increase in frequency is experienced as an increase in pitch by Person B
  • This is the Doppler Effect

IGCSE Physics (7 decks)

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