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Physics 8 > Waves and electromagnetic energy > Flashcards

Waves and electromagnetic energy Flashcards

1
Q

What is a wave?

A

It is a disturbance caused by the vibration of particles in a medium

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2
Q

What is a medium?

A

It is a substance through which the wave travels. When a wave passes through a medium, the medium is only temporarily displaced. Ex: Air for sound waves

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3
Q

What are the properties of waves?

A
  1. Amplitude
  2. Frequency
  3. Time period
  4. Wavelength
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4
Q

Properties of waves:
What is Amplitude?

A

It is the maximum displacement of a wave on either side of its mean position. Its SI unit is Metre (m). The amplitude of a wave often determines its strength or intensity.

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5
Q

Properties of waves:
What if frequency?

A

The number of cycles of a wave in 1 second or the number of vibrations per second. Its SI unit is Hertz (Hz)`

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6
Q

Properties of waves:
What is the time period?

A

It is the time taken for one complete oscillation. (T) is the time it takes the object to return to its exact starting point and direction. It is measured in seconds.

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7
Q

What are the types of waves?

A
  1. Longitudinal waves:
    The vibration of the medium is in the same direction as the wave motion. They produce compressions and rarefactions. Ex: Sound waves
  2. Transverse waves:
    The vibration of the medium is perpendicular to the direction of motion. Produce crests and troughs. Ex: Pulling a guitar string
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8
Q

Properties of waves:
What is wavelength

A

It is the distance between two consecutive crests or troughs. It is measured in meters. It is denoted by Lambda (λ)

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9
Q

Describe electromagnetic waves and electromagnetic radiation.

A

Electromagnetic waves are waves that consist of vibrating electric and magnetic fields. They transfer energy from one place to another.
The transfer of energy by electromagnetic waves is called electromagnetic radiation. Electromagnetic waves can transfer energy through matter or across empty space.

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10
Q

Describe the electric and magnetic fields of an electromagnetic wave

A

The electric and magnetic fields of an electromagnetic wave are areas of electric or magnetic force in which their properties take place. The fields can exert force over objects at a distance.

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11
Q

How does an electromagnetic wave begin?

A

An electromagnetic wave begins when an electrically charged particle vibrates. This causes a vibrating electric field which in turn creates a vibrating magnetic field. The two vibrating fields together form an electromagnetic wave.

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12
Q

How does an electromagnetic wave travel?

A

An electromagnetic wave is a transverse wave that can travel across space and through matter. When it travels through space, it doesn’t lose energy to a medium, but a mechanical wave does.

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13
Q

How do electromagnetic waves interact with matter?

A

When an electromagnetic wave strikes matter, it may be reflected, refracted, or diffracted. Or they may be absorbed by matter and converted to other forms of energy.

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14
Q

What are the sources of electromagnetic waves?

A

The most important source of electromagnetic waves is the sun. Many other sources of electron magnetic waves depend on technology.

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15
Q

What are the properties of electromagnetic waves?

A
  1. All electromagnetic waves travel across space at the speed of light, which is 3*10^8 m/s
  2. Electromagnetic waves may vary in wavelength and frequency. Longer wavelength electromagnetic waves have lower frequencies and vice versa.
  3. The energy of an electromagnetic wave depends on its frequency.
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16
Q

Relationship between speed, wavelength, and frequency:
Speed formula

A

Speed = Wavelength * Frequency.

17
Q

Relationship between speed, wavelength and frequency:
Wavelength formula?

A

Wavelength = Speed/frequency

18
Q

Relationship between speed, wavelength and frequency:
Frequency formula

A

Frequency = Speed / Wavelength.

19
Q

What is electromagnetic spectrum?

A

Sunlight contains the complete range of wavelengths on electromagnetic waves, which is called the electromagnetic spectrum.

20
Q

What are light waves?

A

They are electromagnetic waves that fall roughly in the middle of the electromagnetic spectrum. Light includes infrared light, visible light, and ultraviolet light.

21
Q

What is infrared light?

A

Light with the longest wavelength is called infrared light. The term infrared red means below red. Infrared light is the range of light waves that have longer wavelengths and lower frequencies. Sun gives off infrared light as do flames and living things. You can’t see the infrared light but u can feel it as heat.

22
Q

What are some of the applications of infrared lights.

A
  1. Used in infrared cameras for nighttime photography.
  2. For Therapeutic purposes
  3. Remotes as sensors
  4. Can travel in fog and mist.
23
Q

What is visible light

A

The only light that people can see is called visible light. The light consists of a very narrow range of wavelengths that falls between infrared light and ultraviolet light. Within the visible range we see light of different wavelengths as different colors of light. From red light which has the longest wavelength to violet light that has the shortest wavelength. As they are in sunlight visible light appears white.

24
Q

What is ultraviolet light?

A

Light with wavelengths shorter than visible light is called ultraviolet light. It is the range of light waves that have shorter wavelength and higher frequencies than violet light in the visible light range. It has more energy as it has a higher frequency.

25
Q

Applications of ultraviolet light

A
  1. Can be used to kill bacteria in food
  2. To sterilize surgical instruments
    3, Rich in vitamin D that is important for skin etc.
26
Q

What is energy?

A

It is the ability to do work. Forms of energy are:
1. Chemical energy
2. Luminous energy
3. Nuclear energy
4. Radiant energy
5. Sound energy
6. Thermal energy

27
Q

What is the law of conservation of energy?

A

The law of conservation of energy states that energy can neither be created nor destroyed, only it changes from one form to another.

28
Q

Compare analog and digital signals

A

Analog signals:
1. Analog signals are continuous
2. Denoted by sine (curvy) waves.
Ex: Human voices in air, record player, etc.

Digital signals
1. Digital signals are discrete (binary)
2. Denoted by square (block) waves
Ex: Computer, CD, DVD, MP3 etc.

29
Q

What are the advantages of analog signals?

A

Tape records have been proven to be useful. Records and record albums have an artistic value.

30
Q

Disadvantages of analog signals?

A

Tape/Record players are hard to find. A tape (audio or video) can break. Copying a tape can deteriorate its quality.

31
Q

Advantages of digital signals?

A
  1. Can save more data in a smaller space
  2. No degradation of data
  3. Data can be shared electronically
  4. Data can be stored remotley
32
Q

Disadvantages of digital signals?

A
  1. Computer crash would result in loss of data
  2. Software needs to be unto date
  3. Data can get corrupted or hacked.
  4. Technology can change making access to the data difficult
32
Q

What is sound?

A

It is a form of energy emitted by a vibrating source and transmitted by a material medium .

33
Q

What are sound waves?

A

They are waves carrying sound energy. They can be considered propagation of pressure or density variations in a medium. They are longitudinal waves.

34
Q

What is an echo?

A

It is a phenomenon of repetition of sound of a source by reflection from an obstacle after the original sound ceases off. The sensation of sound lasts in out brain for 0.1 seconds, this property is called persistence of hearing. When sound is repeatedly reflected from a number of obstacles at suitable distances, many echoes are heard one after the other.

35
Q

What are the conditions for a echo to be produced?

A

The minimum distance between the observer and the obstacle should be 17.2 meters. To hear a distant echo the interval between the original and the reflected sound should be 0.1 second. The size of the reflector must be larger than the wavelength of the incident sound.

36
Q

What is echo cardiography?

A

It is used to study the heart and its functions

37
Q

What is Sonar?

A

Sonar is sound navigation and ranging. Geologists use sound waves to identify geological features under the surface of the Earth. Waves are sent through the ground and bounce back to special devices that measure the materials under earth.
It is also used to measure the depth of the sea called the Echo depth ranging.

Physics 8 (5 decks)

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